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The fructose-1,6-bisphosphate aldolase (FBA) gene family exists in higher plants, with the genes of this family playing significant roles in plant growth and development, as well as response to abiotic stresses. However, systematic reports on the FBA gene family and its functions in cucumber are lacking. In this study, we identified five cucumber FBA genes, named CsFBA1-5, that are distributed randomly across chromosomes. Phylogenetic analyses involving these cucumber FBAs, alongside eight Arabidopsis FBA proteins and eight tomato FBA proteins, were conducted to assess their homology. The CsFBAs were grouped into two clades. We also analyzed the physicochemical properties, motif composition, and gene structure of the cucumber FBAs. This analysis highlighted differences in the physicochemical properties and revealed highly conserved domains within the CsFBA family. Additionally, to explore the evolutionary relationships of the CsFBA family further, we constructed comparative syntenic maps with Arabidopsis and tomato, which showed high homology but only one segmental duplication event within the cucumber genome. Expression profiles indicated that the CsFBA gene family is responsive to various abiotic stresses, including low temperature, heat, and salt. Taken together, the results of this study provide a theoretical foundation for understanding the evolution of and future research into the functional characterization of cucumber FBA genes during plant growth and development.

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Fructose 1,6-bisphosphate aldolase (FBA) is a pivotal enzyme, which plays a critical role in fixing CO2 through the process of in the Calvin cycle. In this study, a comprehensive exploration of the FBA family genes in moso bamboo (Phyllostachys edulis) was conducted by the bioinformatics and biological analyses. A total of nine FBA genes (PeFBA1-PeFBA9) were identified in the moso bamboo genome. The expression patterns of PeFBAs across diverse tissues of moso bamboo suggested that they have multifaceted functionality. Notably, PeFBA8 might play an important role in regulating photosynthetic carbon metabolism. Co-expression and cis-element analyses demonstrated that PeFBA8 was regulated by a photosynthetic regulatory transcription factor (PeGLK1), which was confirmed by yeast one-hybrid and dual-luciferase assays. In-planta gene editing analysis revealed that the edited PeFBA8 mutants displayed compromised photosynthetic functionality, characterized by reduced electron transport rate and impaired photosystem I, leading to decreased photosynthesis rate overall, compared to the unedited control. The recombinant protein of PeFBA8 from prokaryotic expression exhibited enzymatic catalytic function. The findings suggest that the expression of PeFBA8 can affect photosynthetic efficiency of moso bamboo leaves, which underlines the potential of leveraging PeFBA8's regulatory mechanism to breed bamboo varieties with enhanced carbon fixation capability.

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4-Hydroxy-2,5-dimethyl-3 (2H)-furanone (HDMF) is widely used in the food industry as a spice and flavoring agent with high market demand. In this study, fructose-1,6-bisphosphate aldolase (FBA) and triose phosphate isomerase (TPI) were overexpressed in Zygosaccharomyces rouxii in the form of single and double genes, respectively, via electroporation. High-yield HDMF-engineered yeast strains were constructed by combining the analysis of gene expression levels obtained by real-time fluorescence quantitative PCR technology and HDMF production measured by HPLC. The results showed that there was a significant positive correlation between the production of HDMF and the expression levels of the FBA and TPI genes in yeast; the expression levels of the FBA and TPI genes were also positively correlated (p < 0.05). Compared with the wild type (WT), the engineered strains F10-D, T17-D, and TF15-A showed marked increases in HDMF production and FBA and TPI gene expression (p < 0.05) and exhibited great genetic stability with no obvious differences in biomass or colony morphology. In addition, the exogenous addition of d-fructose promoted the growth of Z. rouxii. Among the engineered strains, when fermented in YPD media supplemented with d-fructose for 5 days, TF15-A (overexpressing the FBA and TPI genes) generated the highest HDMF production of 13.39 mg/L, which is 1.91 times greater than that of the wild-type strain. The results above indicated that FBA and TPI, which are key enzymes involved in the process of HDMF biosynthesis by Z. rouxii, positively regulate the synthesis of HDMF at the transcriptional level. d-fructose can be used as a precursor for the biosynthesis of HDMF by engineered yeast in industrial production.

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Fructose-1, 6-bisphosphate aldolase (FBA) plays vital roles in plant growth, development, and response to abiotic stress. However, genome-wide identification and structural characterization of the potato (Solanum tuberosum L.) FBA gene family has not been systematically analyzed. In this study, we identified nine StFBA gene members in potato, with six StFBA genes localized in the chloroplast and three in the cytoplasm. The analysis of gene structures, protein structures, and phylogenetic relationships indicated that StFBA genes were divided into Class I and II, which exhibited significant differences in structure and function. Synteny analysis revealed that segmental duplication events promoted the expansion of the StFBA gene family. Promoter analysis showed that most StFBA genes contained cis-regulatory elements associated with light and stress responses. Expression analysis showed that StFBA3, StFBA8, and StFBA9 showing significantly higher expression levels in leaf, stolon, and tuber under blue light, indicating that these genes may improve photosynthesis and play an important function in regulating the induction and expansion of microtubers. Expression levels of the StFBA genes were influenced by drought and salt stress, indicating that they played important roles in abiotic stress. This work offers a theoretical foundation for in-depth understanding of the evolution and function of StFBA genes, as well as providing the basis for the genetic improvement of potatoes.

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Fructose-1,6-bisphosphate aldolase (FBA) is a pivotal enzyme in various metabolic pathways, including glycolysis, gluconeogenesis, and the Calvin cycle. It plays a critical role in CO2 fixation. Building on previous studies on the FBA gene family in Moso bamboo, our study revealed the biological function of PeFBA6. To identify CSN5 candidate genes, this study conducted a yeast two-hybrid library screening experiment. Subsequently, the interaction between CSN5 and PeFBA6 was verified using yeast two-hybrid and LCI experiments. This investigation uncovered evidence that FBA may undergo deubiquitination to maintain glycolytic stability. To further assess the function of PeFBA6, it was overexpressed in rice. Various parameters were determined, including the light response curve, CO2 response curve, and the levels of glucose, fructose, sucrose, and starch in the leaves of overexpressing rice. The results demonstrated that overexpressed rice exhibited a higher saturation light intensity, net photosynthetic rate, maximum carboxylation rate, respiration rate, and increased levels of glucose, fructose, and starch than wild-type rice. These findings indicated that PeFBA6 not only enhanced the photoprotection ability of rice but also improved the photosynthetic carbon metabolism. Overall, this study enhanced our understanding of the function of FBA and revealed the biological function of PeFBA6, thereby providing a foundation for the development of excellent carbon fixation bamboo varieties through breeding.

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BACKGROUND: Ticks are obligate hematophagous ectoparasites that transmit a variety of pathogens to humans, wildlife and domestic animals. Vaccination is an effective and environmentally friendly method for tick control. Fructose-1,6-bisphosphate aldolase (FBA) is an important glycometabolism enzyme that is a candidate vaccine against parasites. However, the immune protection of FBA in ticks is unclear. METHODS AND RESULTS: The 1092-bp open reading frame (ORF) of FBA from Haemaphysalis longicornis (HlFBA), encoding a 363-amino acid protein, was cloned using PCR methodology. The prokaryotic expression vector pET32a(+)-HlFBA was constructed and transformed into cells of Escherichia coli BL21(DE3) strain for protein expression. The recombinant HlFBA protein (rHlFBA) was purified by affinity chromatography, and the western blot results suggested that the rHlFBA protein was immunogenic. RESULTS: Results of the enzyme-linked immunosorbent assay showed that rabbits immunized with rHlFBA produced a humoral immune response specific to rHlFBA. A tick infestation trial indicated that, compared to the ticks in the histidine-tagged thioredoxin (Trx) group, the engorged tick weight and oviposition of female ticks and egg hatching rate of those in the rHlFBA group was reduced by 22.6%, 45.6% and 24.1%, respectively. Based on the cumulative effect of the these three parameters, the overall immune efficacy of rHlFBA was estimated to be 68.4%. CONCLUSIONS: FBA is a candidate anti-tick vaccine that can significantly reduce the engorged tick weight, oviposition, and egg hatching rate. The use of enzymes involved in glucose metabolism is a new strategy in the development of anti-tick vaccines.

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In the present study, the structure of the fructose-1,6-bisphosphataldolase (FBA) gene in Mytilus galloprovincialis (Lamarck, 1819) was analyzed and its tissue specificity of expression level and activity was determined. A 1092 base pairs (bps) complete coding sequence of the FBA gene was assembled from M. galloprovincialis transcriptome. Only one gene encoding FBA (MgFBA) was identified in the M. galloprovincialis genome. The length of MgFBA was 363 amino acids with a molecular mass of 39.7 kDa. According to the amino acid residues, the detected MgFBA gene is a type I aldolase. The FBA gene in M. galloprovincialis had 7 exons; the maximum intron length was about 2.5 kbps. Intraspecific nucleotide diversity (15 mutations) between MgFBAs from the Mediterranean mussels and the Black Sea mussels (present study) was detected. All mutations were synonymous. Tissue specificity in FBA expression level and activity was established. No direct correlation between these functions was found. The highest level of FBA gene expression is found in muscle tissue. According to the phylogenetic analyses, FBA gene in invertebrates could be considered the ancestral gene of muscle type aldolase, which may explain the character of tissue-specific expression.

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Fructose-1,6-bisphosphate aldolase (EC 4.1.2.13) is a highly conserved enzyme that is involved in glycolysis and gluconeogenesis. In this study, we cloned the fructose-1,6-bisphosphate aldolase gene from Euphausia superba (EsFBA). The full-length cDNA sequence of EsFBA is 1098 bp long and encodes a 365-amino-acid protein. The fructose-1,6-bisphosphate aldolase gene was expressed in Escherichia coli (E. coli). A highly purified protein was obtained using HisTrap HP affinity chromatography and size-exclusion chromatography. The predicted three-dimensional structure of EsFBA showed a 65.66% homology with human aldolase, whereas it had the highest homology (84.38%) with the FBA of Penaeus vannamei. Recombinant EsFBA had the highest activity at 45 °C and pH 7.0 in phosphate buffer. By examining the activity of metal ions and EDTA, we found that the effect of metal ions and EDTA on EsFBA's enzyme activity was not significant, while the presence of borohydride severely reduced the enzymatic activity; thus, EsFBA was confirmed to be a class I aldolase. Furthermore, targeted mutations at positions 34, 147, 188, and 230 confirmed that they are key amino acid residues for EsFBA.

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Fruit-tree rootstock selection is a challenge under a scenario of growing environmental stresses in which the soil and climate are greatly affected. Salinization is an increasing global process that severely affects soil fertility. The selection of rootstocks with the ability to tolerate salt stress is essential. Excised root cultures may be an excellent experimental approach to study stress physiology and a predictive tool to assess possible tolerance. In this study, we show how protein changes in response to salt stress evaluated in excised root cultures of Prunus cerasus (moderate salt-sensitive cultivar) could be representative of these changes in the roots of whole plants. The 2D electrophoresis of root extracts and subsequent spot identification by MALDI-TOF/TOF-MS show 16 relevant proteins differentially expressed in roots as a response to 60 mM NaCl. Cytoplasmic isozyme fructose 1,6-bisphosphate aldolase shows relevant changes in its relative presence of isoforms as a response to saline stress, while the total level of enzymes remains similar. Ferredoxin-NADP+ reductase increases as a response to salinity, even though the measured activity is not significantly different. The observed changes are congruent with previous proteomic studies on the roots of whole plants that are involved in protection mechanisms against salt stress.

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Eimeria tenella (E. tenella) is a protozoal parasite that can cause severe cecal lesions and death in chickens, seriously harming the chicken industry. Conventional control strategies mainly rely on anticoccidial drugs. However, the emerging problems of anticoccidial resistance and drug residues necessitate exploring potential drug targets for developing new anticoccidial drugs. Fructose-1,6-bisphosphate aldolase (ALD) is an essential enzyme for parasite energy metabolism that has been considered a potential drug target. In this study, we analyzed the molecular and biochemical properties of E. tenella ALD2 (EtALD2). EtALD2 mRNA expression was highest in second-generation merozoites, whereas the protein level was highest in unsporulated oocysts. Indirect immunofluorescence showed that EtALD2 was mainly distributed in sporozoite' cytoplasm. The natural product inhibitor (morin) was screened by computer-aided drug screening. Enzyme kinetic and inhibition kinetic assays showed that morin had a good inhibitory effect on EtALD2 activity (IC50 = 10.37 µM, Ki = 48.97 µM). In vitro inhibition assay demonstrated that morin had an inhibitory effect on E. tenella development, with an IC50 value of 3.98 µM and drug selection index of 177.49. In vivo, morin significantly improved cecal lesions (p < 0.05) and reduced oocyst excretion (p < 0.05) in E. tenella-infected chickens compared with the untreated group. The anticoccidial index of the group receiving 450 mg morin per kg feed was 162, showing a good anticoccidial effect. These findings suggest that EtALD2 could be a novel drug target for E. tenella treatment, and morin should be further evaluated as a therapeutic candidate for chicken coccidiosis.

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Necrotic enteritis (NE) is a multifactorial and important enteric infectious disease etiologically caused by pathogenic C. perfringens infection, accounting for the estimated loss of around USD 6 billion in the global poultry industry. The increasing incidence of NE was found to be associated with the voluntary reduction or withdrawal of antibiotic growth promoters from animal feed during recent years. Therefore, the development of effective vaccines specific to NE assumes a priority for the poultry industry. This study aimed to identify the potential C. perfringens proteins as vaccine targets for NE. Three recombinant C. perfringens proteins targeting five antigens were prepared: two chimeric proteins (alpha-toxin and NetB, fructose-1,6-bisphosphate aldolase (FBA) and a zinc metalloprotease (Zm)), and one single collagen adhesion protein (Cna). Their protection efficacies were evaluated with a potent challenge model of Eimeria maxima/C. perfringens dual infections using a netB+tpeL+ C. perfringens strain. Young chicks were immunized twice subcutaneously with adjuvanted C. perfringens proteins on Days 4 and 15. At six days after the second immunization, the chickens immunized with Cna, FBA, and Zm antigens, and alpha-toxin had much higher serum antibody titers than unvaccinated controls prior to the challenge. Following the challenge, the pooled antigen-immunized group demonstrated no mortality and the least lesion scores against virulent challenge. The results indicate that the immunization with multicomponent antigens, including C. perfringens housekeeping protein Cna, may confer partial protection.

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Tomato (Solanum lycopersicum) is one of the most important greenhouse vegetables, with a large cultivated area across the world. However, in northern China, tomato plants often suffer from low-temperature stress in solar greenhouse cultivation, which affects plant growth and development and results in economic losses. We previously found that a chloroplast aldolase gene in tomato, SlFBA4, plays an important role in the Calvin-Benson cycle (CBC), and its expression level and activity can be significantly altered when subjected to low-temperature stress. To further study the function of SlFBA4 in the photosynthesis and chilling tolerance of tomato, we obtained transgenic tomato plants by the over-expression and RNA interference (RNAi) of SlFBA4. The over-expression of SlFBA4 led to higher fructose-1,6-bisphosphate aldolase activity, net photosynthetic rate (Pn) and activity of other enzymes in the CBC than wild type. Opposite results were observed in the RNAi lines. Moreover, an increase in thousand-seed weight, plant height, stem diameter and germination rate in optimal and sub-optimal temperatures was observed in the over-expression lines, while opposite effects were observed in the RNAi lines. Furthermore, over-expression of SlFBA4 increased Pn and enzyme activity and decreased malonaldehyde (MDA) content under chilling conditions. On the other hand, Pn and MDA content were more severely influenced by chilling stress in the RNAi lines. These results indicate that SlFBA4 plays an important role in tomato growth and tolerance to chilling stress.

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The Gram-positive Bacillus methanolicus shows plasmid-dependent methylotrophy. This facultative ribulose monophosphate (RuMP) cycle methylotroph possesses two fructose bisphosphate aldolases (FBA) with distinct kinetic properties. The chromosomally encoded FBAC is the major glycolytic aldolase. The gene for the major gluconeogenic aldolase FBAP is found on the natural plasmid pBM19 and is induced during methylotrophic growth. The crystal structures of both enzymes were solved at 2.2 Å and 2.0 Å, respectively, and they suggested amino acid residue 51 to be crucial for binding fructose-1,6-bisphosphate (FBP) as substrate and amino acid residue 140 for active site zinc atom coordination. As FBAC and FBAP differed at these positions, site-directed mutagenesis (SDM) was performed to exchange one or both amino acid residues of the respective proteins. The aldol cleavage reaction was negatively affected by the amino acid exchanges that led to a complete loss of glycolytic activity of FBAP. However, both FBAC and FBAP maintained gluconeogenic aldol condensation activity, and the amino acid exchanges improved the catalytic efficiency of the major glycolytic aldolase FBAC in gluconeogenic direction at least 3-fold. These results confirmed the importance of the structural differences between FBAC and FBAP concerning their distinct enzymatic properties. In order to investigate the physiological roles of both aldolases, the expression of their genes was repressed individually by CRISPR interference (CRISPRi). The fba C RNA levels were reduced by CRISPRi, but concomitantly the fba P RNA levels were increased. Vice versa, a similar compensatory increase of the fba C RNA levels was observed when fba P was repressed by CRISPRi. In addition, targeting fba P decreased tkt P RNA levels since both genes are cotranscribed in a bicistronic operon. However, reduced tkt P RNA levels were not compensated for by increased RNA levels of the chromosomal transketolase gene tkt C.

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Glycolysis is one of the important ways by which Echinococcus multilocularis acquires energy. Fructose-1, 6-bisphosphate aldolase (FBA) plays an important role in this process, but it is not fully characterized in E. multilocularis yet. The results of genome-wide analysis showed that the Echinococcus species contained four fba genes (FBA1-4), all of which had the domain of FBA I and multiple conserved active sites. EmFBA1 was mainly located in the germinal layer and the posterior of the protoscolex. The enzyme activity of EmFBA1 was 67.42 U/mg with Km and Vmax of 1.75 mM and 0.5 mmol/min, respectively. EmFBA1 was only susceptible to Fe3+ but not to the other four ions (Na+, Ca2+, K+, Mg2+), and its enzyme activity was remarkably lost in the presence of 0.5 mM Fe3+. The current study reveals the biochemical characters of EmFBA1 and is informative for further investigation of its role in the glycolysis in E. multilocularis.

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BACKGROUND: Previous studies have demonstrated the formation of stable complexes between inorganic pyrophosphatase (PPase) and three other Escherichia coli enzymes - cupin-type phosphoglucose isomerase (cPGI), class I fructose-1,6-bisphosphate aldolase (FbaB) and l-glutamate decarboxylase (GadA). METHODS: Here, we determined by activity measurements how complex formation between these enzymes affects their activities and oligomeric structure. RESULTS: cPGI activity was modulated by all partner proteins, but none was reciprocally affected by cPGI. PPase activity was down-regulated upon complex formation, whereas all other enzymes were up-regulated. For cPGI, the activation was partially counteracted by a shift in dimer ⇆ hexamer equilibrium to inactive hexamer. Complex stoichiometry appeared to be 1:1 in most cases, but FbaB formed both 1:1 and 1:2 complexes with both GadA and PPase, FbaB activation was only observed in the 1:2 complexes. FbaB and GadA induced functional asymmetry (negative kinetic cooperativity) in hexameric PPase, presumably by favoring partial dissociation to trimers. CONCLUSIONS: These four enzymes form all six possible binary complexes in vitro, resulting in modulated activity of at least one of the constituent enzymes. In five complexes, the effects on activity were unidirectional, and in one complex (FbaB⋅PPase), the effects were reciprocal. The effects of potential physiological significance include inhibition of PPase by FbaB and GadA and activation of FbaB and cPGI by PPase. Together, they provide a mechanism for feedback regulation of FbaB and GadA biosynthesis. GENERAL SIGNIFICANCE: These findings indicate the complexity of functionally significant interactions between cellular enzymes, which classical enzymology treats as individual entities, and demonstrate their moonlighting activities as regulators.

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The halotolerant cyanobacterium, Halothece sp. PCC 7418, possesses two classes of fructose-1,6-bisphosphate aldolase (FBA): H2846 and H2847. Though class I (CI)-FBA H2846 is thought to be associated with salt tolerance, the regulatory mechanisms, molecular characteristics, and expression profiles between H2846 and class II (CII)-FBA H2847 have scarcely been investigated. Here, we show that the accumulation of the H2846 protein is highly responsive to both up- and down-shock with NaCl, whereas H2847 is constitutively expressed. The activity of CI- and CII-FBA in cyanobacterial extracts is correlated with the accumulation patterns of H2846 and H2847, respectively. In addition, it was found that these activities were inhibited by NaCl and KCl, with CII-FBA activity strikingly inhibited. It was also found that the CI-FBA activity of recombinant H2846 was hindered by salts and that this hindrance could be moderated by the addition of glycine betaine (GB), whereas no moderation occurred with other potential osmoprotectant molecules (proline, sucrose, and glycerol). In addition, a phylogenetic analysis showed that CI-FBAs with higher similarities to H2846 tended to be distributed among potential GB-synthesizing cyanobacteria. Taken together, our results provide insights into the independent evolution of the CI- and CII-FBA gene families, which show distinct expression profiles and functions following salt stress.

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Emerging fungal phytodiseases are a food security threat and novel fungicides are in an urgent need. Herein, a series of isobutyrophenone derivatives were designed and synthesized. The derivatives exhibited excellent fungicidal activities against seven fungi. The structure-activity relationship (SAR) study indicated that the introduction of a bromo group at the position 3 or 5 of the phenyl ring, as well as esterification of the 4-hydroxy with a chloroacetyl group, could substantially increase the antifungal activity and spectrum of the compounds. Among all 23 compounds, 2-bromo-3-hydroxy-4-isobutyryl-6-methylphenyl 2-chloroacetate (12b) showed the highest fungicidal activity against all seven tested fungal pathogens with EC50 values ranging from 1.22 to 39.94 µg/mL and exhibited the most potent inhibition against class II fructose-1,6-bisphosphate aldolase with an IC50 of 3.63 µM. The lead compounds were proven to be safe to NIH3T3/293 T cells and silkworm larvae, and relatively stable under different harsh conditions. Detached fruit tests showed the practical potential of lead compounds for fruit (or plant) protection. Taken together, our results indicated that the isobutyrophenone derivatives could be further optimized and developed as advanced leads for new fungicides.

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Fructose-1,6-bisphosphate aldolase (FBA) is a key metabolic enzyme, which is involved in glycolysis, gluconeogenesis and the Calvin cycle. The distinct physiological roles of FBAs in various organisms have been reported; however, in cyanobacteria, the functional characterization of FBAs and investigation of the intracellular dynamics of FBAs largely remains unknown. Here, we utilized a two-step chromatographic technique to identify a class I FBA (CI-FBA), which we named H2846. H2846 was induced by salt stress in the halotolerant cyanobacterium Halothece sp. PCC 7418 (hereafter referred to as Halothece 7418). Phylogenetic analysis showed that H2846-like CI-FBAs existed mainly in cyanobacterial species that inhabit hypersaline environments. Subcellular fractionation revealed that H2846 localized in the cytosolic and periplasmic spaces and size-exclusion chromatography suggested that H2846 formed a homohexamer. The CI-FBA activity of recombinant H2846-mediated cleavage of fructose bisphosphate (FBP) was characterized using a coupled enzymatic assay. This analysis allowed us to determine the Km and Vmax values of recombinant H2846, which were then compared to previously reported Km and Vmax values of several FBAs. Our data suggested that H2846 was likely responsible for the salt stress-induced CI-FBA activity from the total soluble protein extracts derived from Halothece 7418 cells. Moreover, heterologous expression of H2846 but not H2847, a class II FBA (CII-FBA), conferred salt stress tolerance to the salt-sensitive freshwater cyanobacterium, Synechococcus elongatus PCC 7942, which only contains the CII-FBA, S1443. S. elongatus PCC 7942 with a S1443 gene deletion was complemented by H2847 expression, but was not complemented by expression of H2846. Taken together, these results indicate the functional differences between two distinct sets of FBAs in cyanobacteria. H2846 is an active CI-FBA that contributes to the mechanism of salt stress tolerance in Halothece 7418.

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Paracoccidioidomycosis (PCM), caused by thermodimorphic fungi of the Paracoccidioides genus, is a systemic disorder that involves the lungs and other organs. The adherence of pathogenic microorganisms to host tissues is an essential event in the onset of colonization and spread. The host-pathogen interaction is a complex interplay between the defense mechanisms of the host and the efforts of pathogenic microorganisms to colonize it. Therefore, the identification of fungi proteins interacting with host proteins is an important step understanding the survival strategies of the fungus within the host. In this paper, we used affinity chromatography based on surface proteomics (ACSP) to investigate the interactions of pathogen proteins with host surface molecules. Paracoccidioides lutzii extracts enriched of surface proteins were captured by chromatographic resin, which was immobilized with macrophage cell surface proteins, and identified by mass spectrometry. A total of 215 proteins of P. lutzii were identified interacting with macrophage proteins. In silico analysis classified those proteins according to the presence of sites for N- and O-glycosylation and secretion by classical and non-classical pathways. Serine proteinase (SP) and fructose-1,6-bisphosphate aldolase (FBA) were identified in our proteomics analysis. Immunolocalization assay and flow cytometry both showed an increase in the expression of these two proteins during host-pathogen interaction.

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This paper describes a mutant (called SB1707) of the Rhodobacter capsulatus wild type strain SB1003 in which a transposon-disrupted rcc01707 gene resulted in a ∼25-fold increase in the accumulation of coproporphyrin III in the medium of phototrophic (anaerobic) cultures grown in a yeast extract/peptone medium. There was little or no stimulation of pigment accumulation in aerobic cultures. Therefore, this effect of rcc01707 mutation appears to be specific for the anaerobic coproporphyrinogen III oxidase HemN as opposed to the aerobic enzyme HemF. The protein encoded by rcc01707 is homologous to Class I fructose 1,6-bisphosphate aldolases, which catalyze a glycolytic reaction that converts fructose 1, 6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, precursors of pyruvate. There were significant differences in coproporphyrin III accumulation using defined media with individual organic acids and sugars as the sole carbon source: pyruvate, succinate and glutamate stimulated accumulation the most, whereas glucose suppressed coproporphyrin III accumulation to 10% of that of succinate. However, although quantitatively lesser, similar effects of carbon source on the amount of accumulated pigment in the culture medium were seen in a wild type control. Therefore, this mutation appears to exaggerate effects also seen in the wild type strain. It is possible that mutation of rcc01707 causes a metabolic bottleneck or imbalance that was not rectified during growth on the several carbon sources tested. However, we speculate that, analogous to other fructose 1,6-bisphosphate aldolases, the rcc01707 gene product has a "moonlighting" activity that in this case is needed for the maximal expression of the hemN gene. Indeed, it was found that the rcc01707 gene is needed for maximal expression of a hemN promoter-lacZ reporter. With the decrease in hemN expression due to the absence of the rcc01707 gene product, coproporphyrinogen III accumulates and is released from the cell, yielding the spontaneous oxidation product coproporphyrin III.