Correlation between the g Tensors and the Nonplanarity of Porphyrin Rings in Desulfovibrio vulgaris Miyazaki F Cytochrome C_3,Studied by Single Crystal EPR

摘要

Single crystals of cytochrome c_3 from Desulfovibrio vulgaris Miyazaki F were examined by EPR at cryogenic temperature.The principal values and the eigenvectors are determined.The four sets of EPR signals are directly assigned to the specific four hemes in the three-dimensional structure.The relative energy levels of the three d orbitals (d_(xy),d_(xz) and d_(yz)) of each heme iron calculated from the obtained principal g values have shown that the energy gap between dxv and d_(pi) is small for a heme with the S_4-ruffled distortion (heme 1 and heme 2) while the energy gap is large for a heme with the S4-saddled distortion (heme 4).The determined g tensor orientations indicated that the principal g axes of heme 1,heme 2,heme 3,and heme 4 co-rotate with the imidazole planes of the sixth ligands.