Proximal ligand motions in H93G myoglobin

Stefan Franzen, Eric S. Peterson, Derek Brown, Joel M. Friedman, Melissa R. Thomas, Steven G. Boxer

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Resonance Raman spectroscopy has been used to observe changes in the iron-ligand stretching frequency in photoproduct spectra of the proximal cavity mutant of myoglobin H93G. The measurements compare the deoxy ferrous state of the heme iron in H93G(L), where L is an exogenous imidazole ligand bound in the proximal cavity, to the photolyzed intermediate of H93G(L)*CO at 8 ns. There are significant differences in the frequencies of the iron-ligand axial out-of-plane mode ν(Fe-L) in the photoproduct spectra depending on the nature of L for a series of methyl-substituted imidazoles. Further comparison was made with the proximal cavity mutant of myoglobin in the absence of exogenous ligand (H93G) and the photoproduct of the carbonmonoxy adduct of H93G (H93G-*CO). For this case, it has been shown that H2O is the axial (fifth) ligand to the heme iron in the deoxy form of H93G. The photoproduct of H93G-*CO is consistent with a transiently bound ligand proposed to be a histidine. The data presented here further substantiate the conclusion that a conformationally driven ligand switch exists in photolyzed H93G-*CO. The results suggest that ligand conformational changes in response to dynamic motions of the globin on the nanosecond and longer time scales are a general feature of the H93G proximal cavity mutant.

Original languageEnglish (US)
Pages (from-to)4879-4886
Number of pages8
JournalEuropean Journal of Biochemistry
Volume269
Issue number19
DOIs
StatePublished - 2002

Keywords

  • Heme
  • Hemoglobin
  • Ligand switch
  • Myoglobin
  • Resonance Raman

ASJC Scopus subject areas

  • Biochemistry

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