Open AccessEPR study of the redox interactions in cytochrome c 3 from Desulfovibrio vulgaris Miyazaki
Author(s) -
BENOSMAN Haféda,
ASSO Marcel,
BERTRAND Patrick,
YAGI Tatsuhiko,
GAYDA JeanPierre
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb14799.x
Subject(s) - desulfovibrio vulgaris , redox , redox titration , heme , chemistry , cytochrome , desulfovibrio , cytochrome c , titration , electron paramagnetic resonance , hemeprotein , crystallography , analytical chemistry (journal) , stereochemistry , nuclear magnetic resonance , inorganic chemistry , biochemistry , physics , chromatography , biology , organic chemistry , genetics , bacteria , sulfate , mitochondrion , enzyme
We present a new examination of the EPR redox titration data for the tetraheme cytochrome c 3 from Desulfovibrio vulgaris Miyazaki. Our analysis includes the contribution of the interaction potentials between the four redox sites and is based on the model previously developed for the study of cytochrome c 3 from Desulfovibrio desulfuricans Norway. We observed, as for D. desulfuricans Norway cytochrome c 3 , that the conformation of the heme with the lowest redox potential, heme 4, is sensitive to the redox state of the heme with the highest potential, heme 1. However in D. vulgaris Miyazaki cytochrome c 3 spectral simulations show that heme 4 is present in two conformational states which interconvert partially when heme 1 is reduced. The sets of redox parameters which satisfy the fitting procedure of the titration curves are in the following domain: –250 mV ≤ e 1 4 ≤–220 mV, –325 mV ≤ e 2 ≤–320 mV, –335 mV ≤ e 3 ≤–330 mV, –360 mV ≤ e 4 ≤–355 mV, –5 mV ≤ I 12 ≤ 20 mV, –10 mV ≤ I 13 ≤ 5 mV, –15 mV ≤ I 23 ≤–5 mV, –15 mV ≤ I 24 ≤–10 mV, –25 mV ≤ I 34 ≤–15 mV. As in D. desulfuricans Norway cytochrome c 3 the interactions are moderate. Simple electrostatic considerations suggest that these moderate values could be related to the large accessibility of the hemes to the solvent. Our work does not confirm the existence of a cooperative interaction between heme 2 and heme 3 which has been proposed on the basis of electrochemical measurements.