PMID:7492552
| Citation |
Wang, J, Rumbley, J, Ching, YC, Takahashi, S, Gennis, RB and Rousseau, DL (1995) Reaction of cytochrome bo3 with oxygen: extra redox center(s) are present in the protein. Biochemistry 34:15504-11 |
|---|---|
| Abstract |
The reaction of oxygen with cytochrome bo3, a quinol oxidase from Escherichia coli, has been studied by resonance Raman scattering after initiation of the reaction by CO photolysis in a continuous flow apparatus and by directly mixing the enzyme with oxygen. The high-frequency region of the spectrum was monitored to determine the time evolution of the spin, oxidation, and coordination states of heme O and the oxidation state of heme B by using newly established marker lines for each heme. Three phases of the reaction were detected. In phase I, complete in 75 microseconds, O2 reacted with heme O and formed a low-spin ferric or ferryl adduct without significant oxidation of heme B. In phase II, between 75 and 120 microseconds, a small fraction of heme B was oxidized. In phase III, at approximately 1 s, the majority of heme B was oxidized and heme O reverted to a high-spin ferric state. The high rate of oxygen reduction at heme O to the three- or four-electron reduced level, despite a very low rate of heme B oxidation, indicates that there are electron donors active in the enzyme other than the metal centers. Assays of our enzyme preparations rule out a quinol in the tight binding (QH) site as a possible donor but instead suggest electron donation from the protein matrix, such as from tryptophans or tyrosine.(ABSTRACT TRUNCATED AT 250 WORDS) |
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| Keywords |
Computer Simulation; Cytochromes/chemistry; Cytochromes/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Oxidation-Reduction; Oxygen/metabolism; Spectrum Analysis, Raman |
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