THE FORMATE DEHYDROGENASE-CYTOCHROME C(553) COMPLEX FROM DESULFOVIBRIO-VULGARIS HILDENBOROUGH

The electron transfer between formate dehydrogenase and cytochrome c(5 53) from the anaerobic bacteria Desulfovibrio vulgaris Hildenborough h as been investigated. Parameters of the electron transfer kinetics are reported. The ionic strength dependence of the complex formation has been evidenced. Two mutants of cytochrome c(553) have been obtained us ing site-directed mutagenesis with the substitutions K62E and K62E,K63 E. According to one-dimensional and two-dimensional NMR analysis, the two variants were found to have the same folding pattern as that of th e wild-type cytochrome. The replacements of the lysine residues by aci dic groups have important effects on the affinity between the two oxid oreduction partners. K62 and K63 are essential for recognition between the formate dehydrogenase and the cytochrome c(553). Previous structu ral studies of cytochrome c(553) have demonstrated the involvement of the polypeptide chain in the modulation of the particular low oxidored uction potential of this cytochrome. The present study provides eviden ce that. during the evolution of cytochromes from the anaerobic metabo lism to aerobic respiration and photosynthesis, the electrostatic dist ribution at the recognised encounter surface around the heme is highly conserved in all cytochromes.