Conformational changes in hemoglobin S (βE6V) imposed by mutation of the βGlu7-βLys132 salt bridge and detected by UV resonance raman spectroscopy

Laura J. Juszczak, Christophe Fablet, Veronique Baudin-Creuza, Sophie Lesecq-Le Gall, Rhoda Elison Hirsch, Ronald L. Nagel, Joel M. Friedman, Josée Pagnier

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The impact upon molecular structure of an additional point mutation adjacent to the existing E6V mutation in sickle cell hemoglobin was probed spectroscopically. The UV resonance Raman results show that the conformational consequences of mutating the salt bridge pair, βGlu7-βLys132, are dependent on which residue of the pair is modified. The βK132A mutants exhibit the spectroscopic signatures of the R → T state transition in both the "hinge" and "switch" regions of the α1β2 interface. Both singly and doubly mutated hemoglobin (Hb) βE7A exhibit the switch region signature for the R → T quaternary state transition but not the hinge signature. The absence of this hinge region-associated quaternary change is the likely origin of the observed increased oxygen binding affinity for the Hb βE7A mutants. The observed large decrease in the W3 α14β15 band intensity for doubly mutated Hb βE7A is attributed to an enhanced separation in the A helix-E helix tertiary contact of the β subunits. The results for the Hb A βGlu7-βLys132 salt bridge mutants demonstrate that attaining the T state conformation at the hinge region of the α1β2 dimer interface can be achieved through different intraglobin pathways; these pathways are subject to subtle mutagenic manipulation at sites well removed from the dimer interface.

Original languageEnglish (US)
Pages (from-to)7257-7263
Number of pages7
JournalJournal of Biological Chemistry
Volume278
Issue number9
DOIs
StatePublished - Feb 28 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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