Thioredoxin is a small ubiquitous protein that is involved in the dithiol-disulfide exchange reaction, byway of two cysteine residues located on the molecule surface. In order to elucidate the role of thioredoxin in C...Thioredoxin is a small ubiquitous protein that is involved in the dithiol-disulfide exchange reaction, byway of two cysteine residues located on the molecule surface. In order to elucidate the role of thioredoxin in Chlorobaculum tepidurn, an anaerobic green sulfur bacterium that uses various inorganic sulfur compounds and H2S as electron donors under strict anaerobic conditions for growth, we applied the thioredoxin affinity chromatography method （Motohashi et al., 2001）. In this study, 37 cytoplasmic proteins were captured as thioredoxin target candidates, including proteins involved in sulfur assimilation. Furthermore, six of the candidate proteins were members of the reductive tricarboxylic acid cycle （pyruvate orthophosphate dikinase, pyruvate flavodoxin/ferredoxin oxidoreductase, ^-oxoglutarate synthase, citrate lyase, citrate synthase, malate dehydrogenase）. The redox sensitivity of three enzymes was then examined： citrate lyase, citrate synthase, and malate dehydrogenase, using their recombinant proteins. Based on the information relating to the target proteins, the significance of thioredoxin as a reductant for the metabolic pathway in the anaerobic photosynthetic bacteria is discussed.展开更多
文摘Thioredoxin is a small ubiquitous protein that is involved in the dithiol-disulfide exchange reaction, byway of two cysteine residues located on the molecule surface. In order to elucidate the role of thioredoxin in Chlorobaculum tepidurn, an anaerobic green sulfur bacterium that uses various inorganic sulfur compounds and H2S as electron donors under strict anaerobic conditions for growth, we applied the thioredoxin affinity chromatography method （Motohashi et al., 2001）. In this study, 37 cytoplasmic proteins were captured as thioredoxin target candidates, including proteins involved in sulfur assimilation. Furthermore, six of the candidate proteins were members of the reductive tricarboxylic acid cycle （pyruvate orthophosphate dikinase, pyruvate flavodoxin/ferredoxin oxidoreductase, ^-oxoglutarate synthase, citrate lyase, citrate synthase, malate dehydrogenase）. The redox sensitivity of three enzymes was then examined： citrate lyase, citrate synthase, and malate dehydrogenase, using their recombinant proteins. Based on the information relating to the target proteins, the significance of thioredoxin as a reductant for the metabolic pathway in the anaerobic photosynthetic bacteria is discussed.
