Commonly stabilized cytochromes c from deep-sea Shewanella and Pseudomonas.

Two cytochromes c5 (SBcytc and SVcytc) have been derived from Shewanella living in the deep-sea, which is a high pressure environment, so it could be that these proteins are more stable at high pressure than at atmospheric pressure, 0.1 MPa. This study, however, revealed that SBcytc and SVcytc were more stable at 0.1 MPa than at higher pressure. In addition, at 0.1-150 MPa, the stability of SBcytc and SVcytc was higher than that of homologues from atmospheric-pressure Shewanella, which was due to hydrogen bond formation with the heme in the former two proteins. This study further revealed that cytochrome c551 (PMcytc) of deep-sea Pseudomonas was more stable than a homologue of atmospheric-pressure Pseudomonas aeruginosa, and that specific hydrogen bond formation with the heme also occurred in the former. Although SBcytc and SVcytc, and PMcytc are phylogenetically very distant, these deep-sea cytochromes c are commonly stabilized through hydrogen bond formation.