Resonance raman study on axial ligands of heme irons in cytochrome bd‐type ubiquinol oxidase from Escherichia coli

Abstract

AbstractResonance Raman (RR) spectra of cytochrome bd‐type ubiquinol oxidase enriched with Fe‐isotopes were investigated with excitation at 406.7, 424.0, 427.0, 441.6, and 647.1 nm. The bands of reduced form at 252 and 400 cm−1 were tentatively assigned to vFeHis of high‐spin b595 and vFeMet of low‐spin b558, respectively. The v and δFeOO bands of heme d‐O2 were observed at 566 and ∼445 cm−1, respectively. The vFeCO frequency of heme d‐CO was unusually low (477 cm−1) but the v4 frequency was not of P‐450 type. Therefore, the axial ligand of heme d would not be an ordinary histidine or cysteine. © 1995 John Wiley & Sons, Inc.