RESUMEN
Natural ß-folds manage to fold up successfully. By contrast, attempts to dissect fragments or peptides from well folded ß-sheet proteins have met with insurmountable difficulties. Here we briefly review selected successful cases of intervention on the well-known scaffold of intestinal fatty acid binding protein (IFABP). Lessons from these examples might set guidelines along the design of proteins belonging to this class. Impact of modifications on topology, binding and aggregation is highlighted. With the aid of abridged variants of IFABP we focus on key structural features responsible for the assembly into oligomeric forms or aggregates.
Asunto(s)
Proteínas de Unión a Ácidos Grasos/química , Multimerización de Proteína , Animales , Proteínas de Unión a Ácidos Grasos/metabolismo , Ligandos , Estructura Secundaria de ProteínaRESUMEN
Novel antimicrobial peptides are valuable molecules for developing anti-infective drugs to counteract the contemporary spread of microbial drug-resistance. Here we focus on a novel peptide (RKWVWWRNR-NH2) derived from the fragment 107-115 of the human lysozyme that displays a 20-fold increase in anti-staphylococcal activity. The conformational analysis of this peptide and its interaction with model lipidic phases-as assayed by circular dichroism and fluorescence spectroscopy-show a noteworthy spectral change, which might be related to its anti-staphylococcal activity. The secondary structure of peptide [K(108)W(111)] 107-115 hLz was dramatically affected through a single substitution at position 111 (Ala by Trp). Therefore, this conformational change might improve the interaction of the novel peptide with the bacterial plasma membrane. These results highlight the role of peptide secondary structure and the distribution of polar/nonpolar residues for the effective interaction of this peptide with the bacterial plasma membrane, a key step for triggering its lethal effect. This knowledge may contribute to the rational design of a new generation of antimicrobial peptides with increased efficacy developed from natural sources by simple screening tools.
Asunto(s)
Péptidos Catiónicos Antimicrobianos/química , Péptidos Catiónicos Antimicrobianos/farmacología , Staphylococcus/efectos de los fármacos , Secuencia de Aminoácidos , Dicroismo Circular , Datos de Secuencia Molecular , Espectrometría de Fluorescencia , Agua/químicaRESUMEN
In view of acting as controlled delivery systems for nutritional supplementation, therapy or antioxidant activity at interfaces, alginate films of different copolymer composition and glycerol plasticizer levels were developed in the presence of Ca(2+) for achieving higher stability of L-(+)-ascorbic acid (AA). The ability of the alginate network to preserve AA from hydrolysis, tested by storage under vacuum at 25 °C, only decreased with the relative humidity (RH) increase when alginates were mainly constituted by guluronic-guluronic acid blocks (GG), whereas also decreased with the glycerol level increase when mannuronic-mannuronic acid (MM) and/or alternating guluronic-mannuronic (GM+MG) flexible blocks were present in higher proportions. This result could be probably related to the lower capability of the latter alginate block compositions to immobilize water in the network as they are not able to constitute Ca(2+) mediated junction zones where water molecules are highly retained. Films also studied under air storage showed that even at less favorable conditions of RH and glycerol levels, both GG and GM+MG enriched alginate networks in general preserved AA from oxidation. It also demonstrated that hydrolysis is the principal way by which AA is lost when supported in films.
Asunto(s)
Alginatos/química , Ácido Ascórbico/química , Estabilidad de Medicamentos , Almacenaje de Medicamentos , Glicerol/química , Humedad , Hidrólisis , Oxidación-Reducción , Plastificantes/químicaRESUMEN
Growth hormone (GH) binding to GH receptor (GHR) is the initial step that leads to the physiological functions of the hormone. Proteolytical cleavage of the GHR in humans and rabbits and alternative processing of the GHR transcript in rodents generates circulating growth hormone binding protein (GHBP). Moreover, other GHR truncated forms that result from alternative processing of the GHR mRNA transcript have been described. These GHR short forms are inserted in the plasma membrane but they are unable to transduce the signal. In rodents, membrane associated-GHBP (MA-GHBP), which accounts for a significant proportion of liver GH binding capacity, represents the main GHR short form found in membranes, and may therefore function as a negative form of the receptor. In the present study, GHR and MA-GHBP content in liver were analyzed using mutant and transgenic mice expressing different concentrations of growth hormone to evaluate the correlation between GH levels, body weight (BW), GHR and MA-GHBP expression. It was found that GH deficiency was associated with diminished BW, GHR and MA-GHBP expression, while increased GH concentration led to increased BW, GHR and MA-GHBP expression, but MA-GHBP upregulation was more pronounced than the observed increase in GHR expression. Since GHR and MA-GHBP both contribute to liver GH binding capacity, GH-induced enrichment of the dominant negative form would represent a compensatory mechanism triggered by high levels of the hormone. This attempt to attenuate the effects of supraphysiological concentrations of GH may be critical to reduce or prevent their plausible damaging effects on the organism.
Asunto(s)
Proteínas Portadoras/metabolismo , Hormona del Crecimiento/fisiología , Hígado/metabolismo , Receptores de Somatotropina/metabolismo , Animales , Proteínas Portadoras/análisis , Bovinos , Membrana Celular/química , Femenino , Hormona del Crecimiento/genética , Hígado/química , Ratones , Ratones Transgénicos , Receptores de Somatotropina/análisis , Regulación hacia ArribaRESUMEN
We describe a male patient with a Y202H ornithine transcarbamylase deficiency gene mutation who had pancreatitis while taking a low-protein diet, citrulline, and sodium phenylbutyrate.
Asunto(s)
Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/complicaciones , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/genética , Pancreatitis/etiología , Adolescente , Amilasas/sangre , Enfermedad Crónica , Citrulina/uso terapéutico , Terapia Combinada , Dieta con Restricción de Proteínas/efectos adversos , Nutrición Enteral/efectos adversos , Gastrostomía/efectos adversos , Humanos , Lipasa/sangre , Masculino , Mutación/genética , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/diagnóstico , Enfermedad por Deficiencia de Ornitina Carbamoiltransferasa/terapia , Pancreatitis/sangre , Pancreatitis/enzimología , Fenotipo , Factores de RiesgoRESUMEN
The high-resolution structure of ovine placental lactogen (oPL) and ovine prolactin (oPRL), not yet established in detail, was probed by limited proteolysis with the Glu-specific protease from Staphylococcus aureus V8. While in hGH there were no cleavage sites inside of any of the four alpha-helices, the analysis of the fragments obtained after partial proteolysis of oPL showed a site of cleavage at the putative third helix, suggesting that this helix is partially unwound at this point. The partial proteolysis of the rest of the molecule was compatible with a similar folding pattern for oPL, hGH and pGH, on the basis of the crystal structure of these last hormones. In the case of oPRL, proteolytic cleavage occurred at Glu residues which would be located at the end of the first helix and the beginning of the second in the hGH folding model, suggesting that these helices are shorter in oPRL than in hGH. In order to gain further insight on the folding of these molecules, circular dichroism and intrinsic fluorescence measurements were used to examine the effect of denaturing conditions on oPL and oPRL. After exposure to 6 M guanidine the unfolding of both proteins was completely reversed upon elimination of the denaturing agent. In contrast, exposure to pH 3.0 caused an irreversible decrease in the alpha-helical content in both hormones, most striking for oPL, indicating that this hormone is less stable than oPRL or hGH.