Nitrogen and proton ENDOR of cytochrome d, hemin, and metmyoglobin in frozen solutions

Abstract

Orientation-selected electron nuclear double resonance (ENDOR) spectra have been obtained from iron-linked nitrogens of the d heme of the cytochrome d oxidase complex in frozen solution. Heme d is a high-spin chlorin moiety which exists in the cytochrome d complex located in the inner membrane of Escherichia coli. This complex is a terminal oxidase in the E. coli aerobic respiratory chain. Comparison of the spectra of cytochrome d with hemin and metmyoglobin strongly implies that the d heme does not contain an axial nitrogen ligand. By computer simulation of the ENDOR spectra for each magnetic field, the nitrogen hyperfine interaction matrices and quadrupole coupling tensors to the three heme groups were determined