A COMPARISON OF THE REDOX POTENTIALS OF CYTOCHROME C(3) FROM DESULFOVIBRIO-VULGARIS HILDENBOROUGH WITH THOSE FROM DESULFOVIBRIO-VULGARIS MIYAZAKI-F - EFFECTS OF AMINO-ACID SUBSTITUTIONS ON THE REDOX POTENTIALS

The macroscopic and microscopic redox potentials of cytochrome c(3) fr om Desulfovibrio vulgaris Hildenborough (DvH) were estimated by the co mbined use of H-1 NMR and differential pulse polarography at two ionic strengths. The redox potentials obtained were compared with those of Desulfovibrio vulgaris Miyazaki F (DvMF) to see the effect of amino ac id substitution in the 13 residues. Although the general tendencies ar e similar to each other, there are distinct differences. The average r edox potentials of DvH cytochrome c(3) were lower than those of DvMF b y about 34 mV. The difference in the microscopic redox potentials was significant for hemes 1 and 3. The cooperative interaction between hem es 1 and 2 was larger in DvH cytochrome c(3) than in DvMF cytochrome c (3) and the former was ionic strength dependent. The microscopic redox potentials of DvH cytochrome c(3) increased with an increase of ionic strength. (C) 1997 Elsevier Science S.A.