Modulation of reactivity and conformation within the T-quaternary state of human hemoglobin

The combined use of mutagenesis and sol-gel encapsulation

Uri Samuni, Camille J. Roche, David Dantsker, Laura J. Juszczak, Joel M. Friedman

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

A range of conformationally distinct functional states within the T quaternary state of hemoglobin are accessed and probed using a combination of mutagenesis and sol-gel encapsulation that greatly slow or eliminate the T → R transition. Visible and UV resonance Raman spectroscopy are used to probe the proximal strain at the heme and the status of the α 1β2 interface, respectively, whereas CO geminate and bimolecular recombination traces in conjunction with MEM (maximum entropy method) analysis of kinetic populations are used to identify functionally distinct T-state populations. The mutants used in this study are Hb(Nβ102A) and the α99-α99 cross-linked derivative of Hb(Wβ37E). The former mutant, which binds oxygen noncooperatively with very low affinity, is used to access low-affinity ligated T-state conformations, whereas the latter mutant is used to access the high-affinity end of the distribution of T-state conformations. A pattern emerges within the T state in which ligand reactivity increases as both the proximal strain and the α1β 2 interface interactions are progressively lessened after ligand binding to the deoxy T-state species. The ligation and effector-dependent interplay between the heme environment and the stability of the Trp β37 cluster in the hinge region of the α1β2 interface appears to determine the distribution of the ligated T-state species generated upon ligand binding. A qualitative model is presented, suggesting that different T quaternary structures modulate the stability of different αβ dimer conformations within the tetramer.

Original languageEnglish (US)
Pages (from-to)2820-2835
Number of pages16
JournalBiochemistry
Volume45
Issue number9
DOIs
StatePublished - Mar 7 2006

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Mutagenesis
Polymethyl Methacrylate
Encapsulation
Sol-gels
Conformations
Hemoglobins
Gels
Modulation
Ligands
Heme
Maximum entropy methods
Raman Spectrum Analysis
Entropy
Hinges
Carbon Monoxide
Dimers
Genetic Recombination
Population
Ligation
Raman spectroscopy

ASJC Scopus subject areas

  • Biochemistry

Cite this

Modulation of reactivity and conformation within the T-quaternary state of human hemoglobin : The combined use of mutagenesis and sol-gel encapsulation. / Samuni, Uri; Roche, Camille J.; Dantsker, David; Juszczak, Laura J.; Friedman, Joel M.

In: Biochemistry, Vol. 45, No. 9, 07.03.2006, p. 2820-2835.

Research output: Contribution to journalArticle

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