Redox-coupled Conformational Alternations in Cytochrome c₃ from D. vulgaris Miyazaki F on the Basis of its Reduced Solution Structure

Author： Harada E. Fukuoka Y. Ohmura T. Fukunishi A. Kawai G. Fujiwara T. Akutsu H.

Publisher： Academic Press

ISSN： 0022-2836

Source： Journal of Molecular Biology, Vol.319, Iss.3, 2002-06, pp. : 767-778

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Abstract

Heteronuclear NMR spectroscopy was performed to determine the solution structure of ¹⁵N-labeled ferrocytochromec₃ from Desulfovibrio vulgaris Miyazaki F (DvMF). Although the folding of the reduced cytochromec₃ in solution was similar to that of the oxidized one in the crystal structure, the region involving hemes 1 and 2 was different. The redox-coupled conformational change is consistent with the reported solution structure of D. vulgaris Hildenborough ferrocytochromec₃, but is different from those of other cytochromesc₃. The former is homologous with DvMF cytochromec₃ in amino acid sequence. Small displacements of hemes 1 and 2 relative to hemes 3 and 4 were observed. This observation is consistent with the unusual behavior of the 2¹CH₃ signal of heme 3 reported previously. As shown by the ¹⁵N relaxation parameters of the backbone, a region between hemes 1 and 2 has more flexibility than the other regions. The results of this work strongly suggest that the cooperative reduction of hemes 1 and 2 is based on the conformational changes of the C-13 propionate of heme 1 and the aromatic ring of Tyr43, and the interaction between His34 and His 35 through covalent and coordination bonds.© 2002 Elsevier Science Ltd