An oxygen-sensitive mode in oxygenated wild-type cytochrome P450cam (oxyP450cam) is observed at 401 cm -1 and assigned to the δ(Fe-O-O) bending mode, based upon 16 O 2 , 18 O 2 isotopic shifts (19 cm -1 ) and comparison with Co- and Fe-oxyporphyrin complexes. The detection of this Fe-O-O bending mode has structural implications for enzyme function since its frequency reflects the energies associated with Fe-O-O distortion in oxyhemeprotein active sites. Three body normal coordinate calculations adequately fit the experimental data set with a 125-130°bond angle for the Fe-O-O linkage in oxyP450cam. Observation of low-frequency isotope-sensitive vibrational patterns, some of which are hypothesized to be associated with out-of-plane porphyrin motions are also reported. These patterns, in conjunction with the high frequency of this bending mode and the abnormal isotopic shift of the Fe-O 2 stretching mode, suggest a 'strained' Fe-O-O moiety in oxyP450cam, with comparable mobility to HbO 2 and MbO 2 . Possible sources of this 'strain' and implications for catalytic dioxygen activation in P450cam are discussed.
ASJC Scopus subject areas
- Colloid and Surface Chemistry