Quaternary structure dependence of kinetic hole burning and conformational substates interconversion in hemoglobin

Matteo Levantino, Antonio Cupane, L. Zimányi

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Using a sol-gel encapsulation technique, we have prepared samples of CO saturated human adult hemoglobin locked in the R or T quaternary conformation. We report time-resolved spectra of these samples in the Soret region following flash photolysis, in the time interval ranging from 250 ns to 200 ms and in the temperature interval of 100-170 K. A suitable analysis of the measured difference spectra enables us to obtain the spectral contribution of deoxyHb and HbCO molecules as a function of time and/or of the fraction N(t) of deoxyHb molecules. In our experimental time window geminate CO rebinding to hemoglobin in the T quaternary conformation is about 2 orders of magnitude slower than to hemoglobin in the R conformation: this suggests that the barrier distribution for the CO rebinding, g(H), depends strongly on the protein quaternary structure. In our temperature interval, spectral shifts due to kinetic hole burning (KHB) are present: for HbCO the KHB effect is large in the R conformation and small in the T conformation. For deoxyHb the opposite is true. We attribute the observed behavior to the effect of interconversion between the relevant substates. This effect is stronger for HbCO molecules in the T conformation and for deoxyHb molecules in the R conformation; it confirms the quaternary structure dependence of the hemoglobin energy landscape and suggests enhanced dynamics of ligation intermediate species such as T-state HbCO or R-state deoxyHb.

Original languageEnglish
Pages (from-to)4499-4505
Number of pages7
JournalBiochemistry
Volume42
Issue number15
DOIs
Publication statusPublished - Apr 22 2003

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Conformations
Hemoglobins
Carbon Monoxide
Kinetics
Quaternary Protein Structure
Molecules
Temperature
Photolysis
Polymethyl Methacrylate
Ligation
Gels
Encapsulation
Sol-gels
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Quaternary structure dependence of kinetic hole burning and conformational substates interconversion in hemoglobin. / Levantino, Matteo; Cupane, Antonio; Zimányi, L.

In: Biochemistry, Vol. 42, No. 15, 22.04.2003, p. 4499-4505.

Research output: Contribution to journalArticle

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