Conference paper

Electronic Structure of Cytochrome P450

L. K. Hanson ; Laboratory of Chemical Physics, National Institute of Arthritis, Metabolism and Digestive Diseases, National Institutes of Health, Bethesda, Maryland 20014, U .S.A.
S. G. Sligar ; Department of Biochemistry. University of Illinois, Urbana, Illinois 61801, U .S.A.
I. C. Gunsalus ; Department of Biochemistry. University of Illinois, Urbana, Illinois 61801, U .S.A.

Abstract

The optical properties of P450 have been investigated by means
of polarized absorption spectroscopy of single crystals of camphor-
bound P450CAM in the oxidized, reduced, and CO-reduced states,
and iterative extended Ruckel (IEH) calculations. The heme chromophores
are orientated such that transitions polarized in the heme
plane (x,y-polarized) can be readily distinguished from transitions
polarized perpendicular to the heme plane (z-polarized) . High spin
oxidized P450 exhibits two broad z-polarized bands, at 567 and
323 nm. IEH calculations suggest that these bands arise from
cysteine mercaptide sulfur-to-iron charge transfer transitions.
High spin reduced P450 has no z-polarized bands. IEH calculations
suggest that loss of these bands occurs because the cysteine sulfur
is protonated to a mercaptan. Low spin CO-P450 has an intense
x,y-polarized band at 363 nm. This transition, assigned as a mercaptide
sulfur-to-porphyrin charge transfer transition, has the
correct symmetry to mix with the Soret and may cause the
anomalous red shift of the Soret.

Keywords

Hrčak ID:

196363

URI

https://hrcak.srce.hr/196363

Publication date:

30.3.1977.

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