Ligand binding to heme proteins. V. Light-induced relaxation in proximal mutants L89I and H97F of carbonmonoxymyoglobin

Y. Abadan, E. Y. Chien, K. Chu, C. D. Eng, G. U. Nienhaus, S. G. Sligar

Research output: Contribution to journalArticlepeer-review

Abstract

We have studied the proximal mutants L89I and H97F of MbCO with FTIR and temperature-derivative spectroscopy at temperatures between 10 and 160 K. The mutations give rise only to minor alterations of the stretch spectra of the bound and photodissociated CO ligand. The most pronounced difference is a larger population in the A3 substate at approximately 1930 cm-1 in the mutants. The barrier distributions, as determined by temperature-derivative spectroscopy, are very similar to native MbCO after short illumination. Extended illumination leads to substantial increases of the rebinding barriers in native MbCO and the proximal mutants. A larger fraction of light-relaxed states is found in the proximal mutants, implying that the conformational energy landscape has been modified to more easily allow light-induced transitions. These and other spectroscopic data imply that the large changes in the binding properties are brought about by a light-induced conformational relaxation involving the structure at the heme iron. Similarities with spectral hole-burning studies and physical models are discussed.

Original languageEnglish (US)
Pages (from-to)2497-2504
Number of pages8
JournalBiophysical journal
Volume68
Issue number6
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • Biophysics

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