Characterization of a cytochrome c gene located at the gene cluster for chlorate respiration in Ideonella dechloratans

SummaryAnaerobic chlorate respiration requires electron transport from the bacterial inner membrane to the soluble periplasmic chlorate reductase. We have recently demonstrated that soluble c cytochromes function as electron carriers for chlorate reduction in Ideonella dechloratans ( Smedja Bäcklund et al. 2009). In the present work, we describe a gene encoding soluble c-type cytochrome [cyt; GenBank ID: EU768872] located close to the gene cluster for chlorate reduction in I. dechloratans. The predicted amino acid sequence does not match any of the peptide masses or partial sequences obtained earlier from periplasmic c cytochromes. The gene, without the predicted signal sequence, was expressed heterologously in E. coli and the recombinant protein was purified, refolded and reconstituted with heme. The reconstituted protein shows spectral properties characteristic for c cytochromes, with an absorption maximum at 553 nm for the alpha band in the reduced state. Pyridine hemochrome analysis demonstrates the formation of covalently bound heme.