RESUMEN
Many photosynthetic bacteria use inorganic sulfur compounds as electron donors for carbon dioxide fixation. A thiosulfate-induced cytochrome c has been purified from the photosynthetic alpha-proteobacterium Rhodovulum sulfidophilum. This cytochrome c(551) is a heterodimer of a diheme 30-kDa SoxA subunit and a monoheme 15-kDa SoxX subunit. The cytochrome c(551) structural genes are part of an 11-gene sox locus. Sequence analysis suggests that the ligands to the heme iron in SoxX are a methionine and a histidine, while both SoxA hemes are predicted to have unusual cysteine-plus-histidine coordination. A soxA mutant strain is unable to grow photoautotrophically on or oxidize either thiosulfate or sulfide. Cytochrome c(551) is thus essential for the metabolism of both these sulfur species. Periplasmic extracts of wild-type R. sulfidophilum exhibit thiosulfate:cytochrome c oxidoreductase activity. However, such activity can only be measured for a soxA mutant strain if the periplasmic extract is supplemented with purified cytochrome c(551). Gene clusters similar to the R. sulfidophilum sox locus can be found in the genome of a green sulfur bacterium and in phylogenetically diverse nonphotosynthetic autotrophs.
Asunto(s)
Alphaproteobacteria/metabolismo , Proteínas Bacterianas , Grupo Citocromo c/metabolismo , Fotosíntesis/fisiología , Sulfuros/metabolismo , Tiosulfatos/metabolismo , Secuencia de Aminoácidos , Clonación Molecular , Grupo Citocromo c/genética , Grupo Citocromo c/aislamiento & purificación , Inducción Enzimática , Genes Bacterianos , Biología Marina , Datos de Secuencia Molecular , Mutagénesis Insercional , Oxidación-Reducción , Oxidorreductasas/genética , Periplasma/enzimología , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Microbiología del AguaRESUMEN
A leucine-rich repeat plant protein involved in resistance to pathogens, a polygalacturonase-inhibiting protein (PGIP-1) from Phaseolus vulgaris, has been crystallized and preliminary X-ray characterization has been performed. The protein contains ten repeats of a short (24 amino-acid) leucine-rich repeat motif. Single crystals of the protein were grown from vapour-diffusion experiments using PEG 2K monomethylether as precipitant; these crystals diffract to at least 2.3 A resolution. The space group is P2(1), with two molecules of PGIP-1 in the asymmetric unit; the crystals contain approximately 38% solvent.
Asunto(s)
Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/aislamiento & purificación , Fabaceae/química , Proteínas de Plantas/química , Proteínas de Plantas/aislamiento & purificación , Plantas Medicinales , Poligalacturonasa/antagonistas & inhibidores , Secuencia de Aminoácidos , Cristalización , Cristalografía por Rayos X , Fabaceae/genética , Solanum lycopersicum/genética , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/aislamiento & purificaciónRESUMEN
Arginine and creatine kinase activities in different muscles are compared with calculated maximum rates of ATP turnover. The magnitude of the kinase activities decreases in the following order: anaerobic muscles and vertebrate skeletal muscles greater than heart muscle greater than insect flight muscle. The maximum activity of phosphagen kinases (i.e. creatine kinase and arginine kinase), in the direction of phosphagen formation, is lower than the calculated maximum rate of ATP turnover in insect flight muscle or rat heart.