抄録
A diaphorase protein purified from Bacillus subtilis was found to be the yumC gene product from N-terminal amino acid sequencing. YumC is a homo-dimer of 94kDa with one molecule of FAD per subunit. YumC supports diaphorase activity with higher affinity to NADPH than NADH, low NADPH oxidase activity and ferredoxin oxidoreductase activity. YumC shows high amino acid sequence identity to the novel type FNR from green sulfur bacterium Chlorobium tepidum. A BLAST search with YumC as a query sequence revealed that there are more than 30 genes in prokaryotes coding for similar proteins variously annotated as thoredoxin reductase, NAD(P)H oxidase, etc. These genes are present notably in Gram-positive bacteria except for clostridia, and less frequently in Archaea and proteobacteria. We propose that YumC together with C. tepidum FNR constitute a new group of FNR, which should be added to already established plant type, bacteria type, and mitochondria type FNR groups.
