Comparison of the resonance raman properties of the fast and slow forms of cytochrome oxidase
Resonance Raman (RR) spectra of the rapid and slow forms 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 a/sub 3/ upon conversion to the slow form. In the low-frequency region a peak present at 223 cm/sup -1/ in the rapid form shifts to 220 cm/sup -1/ in the slow form; this peak is assigned as the cytochrome a/sub 3/ Fe(III)-N(His-Im) stretch. The slow form of the enzyme possesses greater intensity in RR peaks near 1620 cm/sup -1/ which have been previously attributed by others to partial photoreduction of the enzyme. The authors 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/sup -1/ features are unreliable indicators of photoreduction. The spectra of the fast- and slow-reacting species in H/sub 2/O and D/sub 2/O have been compared. These deuterium shifts are not observed in the slow form. They suggest that the nature of the difference between the fast and slow forms of the enzyme is a global conformational change involving inter alia the axial histidine ligand of cytochrome a/sub 3/ and the cytochrome a environment. This conformational change is also responsible for the enhanced Raman intensity observed at 1620 cm/sup -1/ in the slow form. Some mechanisms whereby such a conformational change might affect the cytochrome a/sub 3/ Soret energy are discussed.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- OSTI ID:
- 6828081
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 27:15; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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62 RADIOLOGY AND NUCLEAR MEDICINE
ANIMALS
BODY
CARDIOVASCULAR SYSTEM
CATTLE
CONFORMATIONAL CHANGES
CYTOCHROME OXIDASE
DOMESTIC ANIMALS
ENZYMES
HAEM DEHYDROGENASES
HEART
HEAVY WATER
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
LIGANDS
MAMMALS
ORGANS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
RAMAN SPECTRA
RAMAN SPECTROSCOPY
RUMINANTS
SPECTRA
SPECTROSCOPY
VERTEBRATES
WATER