Properties of human hemoglobins with increased polarity in the α- or β-heme pocket: Carbonmonoxy derivatives

Michael Karavitis, Clara Fronticelli, William S. Brinigar, Gregory B. Vasquez, Valeria Militello, Maurizio Leone, Antonio Cupane

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The spectroscopic, conformational, and functional properties of mutant carbonmonoxy hemoglobins in which either the β-globin Val67(E11) or the α-globin Val62(E11) is replaced by threonine have been investigated. The thermal evolution of the Sorer absorption band and the stretching frequency of the bound CO were used to probe the stereodynamic properties of the heme pocket. The functional properties were investigated by kinetic measurements. The spectroscopic and functional data were related to the conformational properties through molecular analysis. The effects of this nonpolar-to-polar isosteric mutation are: (i) increase of heme pocket anharmonic motions, (ii) stabilization of the A(o) conformer in the IR spectrum, (iii) increased CO dissociation rates. The spectroscopic data indicate that for the carbonmonoxy derivatives, the Val → Thr mutation has a larger conformational effect on the β-subunits than on the α-subunits. This is at variance with the deoxy derivatives where the conformational modification was larger in the heme pocket of the α-subunit (Cupane, A., Leone, M., Militello, V., Friedman, R. K., Koley, A. P., Vasquez, G. P., Brinigar, W. S., Karavitis, M., and Fronticelli, C. (1997) J. Biol. Chem. 272, 26271-26278). These effects are attributed to a different electrostatic interaction between O(γ) of Thr(E11) and the bound CO molecule. Molecular analysis indicates a more favorable interaction of the bound CO with Thr O(γ) in the β-subunit heme pocket.

Original languageEnglish (US)
Pages (from-to)23740-23749
Number of pages10
JournalJournal of Biological Chemistry
Issue number37
StatePublished - Sep 11 1998
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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