Spectroscopically and kinetically distinct conformational populations of sol-gel-encapsulated carbonmonoxy myoglobin: A comparison with hemoglobin

Uri Samuni, David Dantsker, Imran Khan, Adam J. Friedman, Eric Peterson, Joel M. Friedman

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

We have used sol-gel encapsulation protocols to trap kinetically and spectroscopically distinct conformational populations of native horse carbonmonoxy myoglobin. The method allows for direct comparison of functional and spectroscopic properties of equilibrium and non-equilibrium populations under the same temperature and viscosity conditions. The results implicate tertiary structure changes that include the proximal heme environment in the mechanism for population-specific differences in the observed rebinding kinetics. Differences in the resonance Raman frequency of v(Fe-His), the iron-proximal histidine stretching mode, are attributed to differences in the positioning of the F helix. For myoglobin, the degree of separation between the F helix and the heme is assigned as the conformational coordinate that modulates both this frequency and the innermost barrier controlling CO rebinding. A comparison with the behavior of encapsulated derivatives of human adult hemoglobin indicates that these CO binding-induced conformational changes are qualitatively similar to the tertiary changes that occur within both the R and T quaternary states. Protein-specific differences in the time scale for the proposed F helix relaxation are attributed to variations in the intra-helical hydrogen bonding patterns that help stabilize the position of the F helix.

Original languageEnglish (US)
Pages (from-to)25783-25790
Number of pages8
JournalJournal of Biological Chemistry
Volume277
Issue number28
DOIs
StatePublished - Jul 12 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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