Crystal structure of the oxidized cytochrome c(2) from Blastochloris viridis.

The crystal structure of the oxidized cytochrome c(2) from Blastochloris (formerly Rhodopseudomonas) viridis was determined at 1.9 A resolution. Structural comparison with the reduced form revealed significant structural changes according to the oxidation state of the heme iron. Slight perturbation of the polypeptide chain backbone was observed, and the secondary structure and the hydrogen patterns between main-chain atoms were retained. The oxidation state-dependent conformational shifts were localized in the vicinity of the methionine ligand side and the propionate group of the heme. The conserved segment of the polypeptide chain in cytochrome c and cytochrome c(2) exhibited some degree of mobility, interacting with the heme iron atom by the hydrogen bond network. These results indicate that the movement of the internal water molecule conserved in various c-type cytochromes drives the adjustments of side-chain atoms of nearby residue, and the segmental temperature factor changes along the polypeptide chain.