RESUMO
The naturally occurring dinorcholanic lactone vespertilin and two other non-natural derivatives bearing the 5α-hydroxy-6-oxo moiety were synthesized starting from the readily available steroid sapogenin diosgenin. The obtained compounds showed plant growth promoting activity in the bean's second internode elongation assay.
Assuntos
Fabaceae/crescimento & desenvolvimento , Lactonas/química , Lactonas/metabolismo , Reguladores de Crescimento de Plantas/química , Reguladores de Crescimento de Plantas/metabolismo , Diosgenina/química , Fabaceae/química , Fabaceae/metabolismo , Lactonas/síntese química , Reguladores de Crescimento de Plantas/síntese química , Sapogeninas/química , Sementes/química , Sementes/crescimento & desenvolvimento , Sementes/metabolismoRESUMO
Three polyhydroxylated ketones bearing the 5α-hydroxy-6-oxo moiety were obtained from cholesterol. Two of them show plant growth promoting activity in the bean's second internode bioassay. The obtained results indicate that the presence of the 5α-hydroxy-6-oxo moiety may be capable to induce plant growth promotion even the absence oxygenated functions in the side chain.
Assuntos
Colestanos/química , Fabaceae/crescimento & desenvolvimento , Cetonas/síntese química , Modelos Químicos , Relação Dose-Resposta a Droga , Fabaceae/efeitos dos fármacos , Hidroxilação , Cetonas/química , Cetonas/farmacologia , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
Two furostanic analogues of brassinosteroids bearing the 5alpha-hydroxy-6-oxo moiety were synthesized and their biological activity studied using the bean second internode elongation test. One of the compounds produced significant stimulation at doses of 2.5 and 5ng/plant.
Assuntos
Reguladores de Crescimento de Plantas/química , Reguladores de Crescimento de Plantas/farmacologia , Esteroides Heterocíclicos/síntese química , Esteroides Heterocíclicos/farmacologia , Colestanonas/farmacologia , Relação Dose-Resposta a Droga , Estrutura Molecular , Phaseolus/efeitos dos fármacos , Phaseolus/crescimento & desenvolvimento , Reguladores de Crescimento de Plantas/síntese química , Sementes/efeitos dos fármacos , Sementes/crescimento & desenvolvimento , Esteroides Heterocíclicos/químicaRESUMO
The ability of Entamoeba histolytica TATA binding protein (EhTBP) to interact with different TATA boxes in gene promoters may be one of the key factors to perform an efficient transcription in this human parasite. In this paper we used several TATA variants to study the in vitro EhTBP DNA-binding activity and to determine the TATA-EhTBP dissociation constants. The presence of EhTBP in complexes formed by nuclear extracts (NE) and the TATTTAAA oligonucleotide, which corresponds to the canonical TATA box for E. histolytica, was demonstrated by gel-shift assays. In these experiments a single NE-TATTTAAA oligonucleotide complex was detected. Complex was retarded by anti-EhTBP Igs in supershift experiments and antibodies also recognized the cross-linked complex in Western blot assays. Recombinant EhTBP formed specific complexes with TATA variants found in E. histolytica gene promoters and other TATA variants generated by mutation of TATTTAAA sequence. The dissociation constants of recombinant EhTBP for TATA variants ranged between 1.04 (+/-0.39) x 10(-11) and 1.60 (+/-0.37) x 10(-10) m. TATTTAAA and TAT_ _AAA motifs presented the lowest KD values. Intriguingly, the recombinant EhTBP affinity for TATA variants is stronger than other TBPs reported. In addition, EhTBP is more promiscuous than human and yeast TBPs, probably due to modifications in amino acids involved in TBP-DNA binding.
Assuntos
Entamoeba histolytica/metabolismo , TATA Box/fisiologia , Proteína de Ligação a TATA-Box/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Sequência Conservada , Variação Genética , Humanos , Cinética , Dados de Sequência Molecular , Mutagênese , Regiões Promotoras Genéticas , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , TATA Box/genética , Proteína de Ligação a TATA-Box/química , Proteína de Ligação a TATA-Box/genéticaRESUMO
A 309 bp DNA fragment from Entamoeba histolytica was amplified by PCR using primers derived from the Acanthamoeba castellanii consensus TATA-box binding protein amino acid sequence. The amplified fragment was used to isolate cDNA and genomic DNA clones containing an ORF encoding the complete E. histolytica TATA-box binding protein (Ehtbp, 702 bp, 234 aa, molecular mass 26 kDa). The EhTBP functional domain showed 55% sequence identity to that of Homo sapiens, 54% to A. castellanii and 37% to Plasmodium falciparum TBPs. In Southern blot experiments we detected a single Ehtbp band, which was transcribed as a 1.3 kb mRNA containing a 420 nt 5' untranslated region. However, the probe hybridized with the 0.8 and 1.5 Mb chromosomes, suggesting that this sequence is diploid. In situ PCR assays showed two signals in 95% of trophozoites, one located in the nucleus and another in EhkO, the novel DNA-containing organelle recently reported. The recombinant E. histolytica TATA-box binding protein was expressed in Escherichia coli. Antibodies against it recognized two proteins of 26 and 29 kDa in E. histolytica nuclear extracts. Confocal microscopy immunofluorescence analysis located the protein in both the nucleus and EhkO.