Modification of α-chain or γ-chain heme pocket polarity by Val(E11) → Thr substitution has different effects on the steric, dynamic, and functional properties of human recombinant hemoglobin. Deoxy derivatives

Antonio Cupane, Maurizio Leone, Valeria Militello, Fred K. Friedman, Aditya P. Koley, Gregory B. Vasquez, William S. Brinigar, Michael Karavitis, Clara Fronticelli

Research output: Contribution to journalArticle

Abstract

The dynamic and functional properties of mutant deoxyhemoglobins in which either the β-globin Val67(E11) or the α-globin Val62(E11) is replaced by threonine have been investigated through the thermal evolution of the Soret absorption band in the temperature range 300 to 20 K and through the kinetics of CO rebinding after flash photolysis at room temperature. The conformational properties of the modified α chain and β chain distal heine pockets were also studied through x-ray crystallography and molecular modeling. The data obtained with the various techniques consistently indicate that the polar isosteric mutation in the distal side of the α chain heme pocket has a larger effect on the investigated properties than the analogous mutation on the β chain. We attribute the observed differences to the presence of a water molecule in the distal heme pocket of the modified a chains, interacting with the hydroxyl of the threonine side chain. This is indicated by molecular modeling which showed that the water molecule present in the α chain distal heme pocket can bridge by H bonding between Thr62(E11) and His58(E7) without introducing any unfavorable steric interactions. Consistent with the dynamic and functional data, the presence of a water molecule in the distal heine pocket of the modified β chains is not observed by x-ray crystallography.

Original languageEnglish (US)
Pages (from-to)26271-26278
Number of pages8
JournalJournal of Biological Chemistry
Volume272
Issue number42
DOIs
StatePublished - Oct 17 1997

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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