Cytochrome c peroxidase complexed with cytochrome c has an unperturbed heme moiety

Jianling Wang, Randy W. Larsen, Susan J. Moench, James D. Satterlee, Denis L. Rousseau, Mark R. Ondrias

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10 Scopus citations

Abstract

Transient resonance Raman, Raman difference, circular dichroism (CD), and optical absorption studies have been carried out on the electrostatic complexes formed by yeast cytochrome c peroxidase (CCP) with horse cytochrome c (Cytc) in low ionic strength solutions. In all the complexes examined [e.g., CCP(II)/Cytc(II), CCP(III)/Cytc(II), CCP(III)/Cytc(III)], the local heme environments of both proteins are largely unperturbed upon complexation. Specifically, CCP preserves a completely pentacoordinate high-spin home in both its ferric and ferrous forms in CCP/Cytc complexes and uncomplexed mixtures. We found no evidence corroborating the previously reported increase in the low-spin fraction of CCP heme upon complexation with Cytc [Hildebrandt et al. (1992) Biochemistry 31, 2384-2392]. Instead, our Raman data strongly suggest that the H-bonding networks in the distal and proximal pockets of CCP are well maintained in the complexes. On the other hand, CD spectra of CCP(III)/Cytc(III) complexes showed substantial variations (relative to the uncomplexed mixtures) in the far-UV region, reflecting some protein conformational rearrangements. In addition, the spectral data suggest that complexation with Cytc affects the previously observed pH-dependent flexibility of the heme structure of CCP and thus influences the photodynamics of the CCP active site.

Original languageEnglish (US)
Pages (from-to)453-463
Number of pages11
JournalBiochemistry
Volume35
Issue number2
DOIs
StatePublished - Jan 16 1996
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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