Structural factors controlling ligand binding to myoglobin: A kinetic hole-burning study

P. Ormos, Sándor Száraz, Antonio Cupane, G. Ulrich Nienhaus

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Using temperature-derivative spectroscopy in the temperature range below 100 K, we have studied the dependence of the Soret band on the recombination barrier in sperm whale carbonmonoxy myoglobin (MbCO) after photodissociation at 12 K. The spectra were separated into contributions from the photodissociated species, Mb*CO, and CO-bound myoglobin. The line shapes of the Soret bands of both photolyzed and liganded myoglobin were analyzed with a model that takes into account the homogeneous bandwidth, coupling of the electronic transition to vibrational modes, and static conformational heterogeneity. The analysis yields correlations between the activation enthalpy for rebinding and the model parameters that characterize the homogeneous subensembles within the conformationally heterogeneous ensemble. Such couplings between spectral and functional parameters arise when they both originate from a common structural coordinate. This effect is frequently denoted as 'kinetic hole burning.' The study of these correlations gives direct insights into the structure-function relationship in proteins. On the basis of earlier work that assigned spectral parameters to geometric properties of the heme, the connections with the heme geometry are discussed. We show that two separate structural coordinates influence the Soret line shape, but only one of the two is coupled to the enthalpy barrier for rebinding. We give evidence that this coordinate, contrary to widespread belief, is not the iron displacement from the mean heme plane.

Original languageEnglish
Pages (from-to)6762-6767
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number12
DOIs
Publication statusPublished - Jun 9 1998

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Myoglobin
Heme
Carbon Monoxide
Ligands
Sperm Whale
Temperature
Genetic Recombination
Spectrum Analysis
Iron
Proteins

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Structural factors controlling ligand binding to myoglobin : A kinetic hole-burning study. / Ormos, P.; Száraz, Sándor; Cupane, Antonio; Nienhaus, G. Ulrich.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 95, No. 12, 09.06.1998, p. 6762-6767.

Research output: Contribution to journalArticle

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