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Cytochrome d axial ligand of the bd-type terminal quinol oxidase from Escherichia coli

Tsubaki, M.; Uno, T.; Hori, H.; Mogi, T.; Nishimura, Y.; Anraku, Y.

Febs Letters 335(1): 13-17

1993


ISSN/ISBN: 0014-5793
PMID: 8243657
DOI: 10.1016/0014-5793(93)80430-3
Accession: 008409413

Using various spectroscopic techniques, we studied the structure of the dioxygen reduction site of the bd-type terminal quinol oxidase in the aerobic respiratory chain of Escherichia coli. Resonance Raman and FT-IR spectroscopies identified the v(Fe(2+)-CO) and v(C-O) stretching frequencies at 471 and 1980.7 cm-1, respectively, at the cytochrome d center of the dithionite-reduced CO-bound enzyme. The CO ligation in the cytochrome bd complex is considerably different from those of the heme-copper terminal oxidases. Anaerobic addition of NO to the air-oxidized enzyme caused an exchange of cytochrome d-bound dioxygen with NO leading to an appearance of cytochrome d-NO EPR signal. But there is no superhyperfine structure originating from the cytochrome d proximal 14N ligand in the central resonance of the NO EPR signal. These results suggest that cytochrome d axial ligand of the cytochrome bd complex is likely a histidine residue in an anomalous condition or other than a histidine residue and, therefore, the molecular structure around the dioxygen-binding site is different from that of the heme-copper terminal oxidases.

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