title: A comparison of the resonance Raman properties of the fast and slow forms of cytochrome oxidase.
abstract: Resonance Raman (RR) spectra of the "rapid" and "slow" forms (Baker et al., 1987) of resting cytochrome oxidase obtained with Soret excitation at 413.1 nm are reported. There are a number of conspicuous differences between the two forms in the high-frequency region of the RR spectrum which involve changes in Raman intensity arising from a blue shift in the Soret maximum of cytochrome a3 upon conversion to the slow form. In the low-frequency region a peak present at 223 cm-1 in the rapid form shifts to 220 cm-1 in the slow form; this peak is assigned as the cytochrome a3 Fe(III)-N(His-Im) stretch. The slow form of the enzyme possesses greater intensity in RR peaks near 1620 cm-1 which have been previously attributed by others to partial photoreduction of the enzyme. We have quantitated the amount of laser-induced photoreduction in these RR spectra by comparison with the spectra of mixed-valence derivatives of the enzyme and find that these 1620-cm-1 features are unreliable indicators of photoreduction. The spectra of the fast- and slow-reacting species in H2O and D2O have been compared. The fast-reacting form exhibits a 4-cm-1 shift, from 223 to 219 cm-1, upon transferring to D2O in a peak which we assign as the cytochrome a3 Fe(III)-N(His-Im) stretch. There is a parallel shift in the feature at 1651 cm-1 due to the C = O stretch of the formyl group of cytochrome a. These deuterium shifts are not observed in the slow form.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Isotope and Structural Chemistry Group (INC-4), Los Alamos National Laboratory, University of California, New Mexico 87545.
authors.forename: J R
authors.initials: JR
authors.lastname: Schoonover
authors.forename: R B
authors.initials: RB
authors.lastname: Dyer
authors.forename: W H
authors.initials: WH
authors.lastname: Woodruff
authors.forename: G M
authors.initials: GM
authors.lastname: Baker
authors.forename: M
authors.initials: M
authors.lastname: Noguchi
authors.forename: G
authors.initials: G
authors.lastname: Palmer
mesh_terms: D000818:Animals; D002642:Chick Embryo; D003903:Deuterium; D003576:Electron Transport Complex IV / Q000145:classification; D007527:Isoenzymes; D007834:Lasers; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D010777:Photochemistry; D013059:Spectrum Analysis, Raman
chemical_list: D007527:Isoenzymes; D003903:Deuterium; D003576:Electron Transport Complex IV