Ultrafast heme-ligand recombination in truncated hemoglobin HbO from Mycobacterium tuberculosis

A ligand cage

Audrius Jasaitis, Hugues Ouellet, Jean Christophe Lambry, Jean Louis Martin, Joel M. Friedman, Michel Guertin, Marten H. Vos

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Truncated hemoglobin HbO from Mycobacterium tuberculosis displays very slow exchange of diatomic ligands with its environment. Using femtosecond spectroscopy, we show that upon photoexcitation, ligands rebind with unusual speed and efficiency. Only ∼1% O 2 can escape from the heme pocket and less than 1% NO. Most remarkably, CO rebinding occurs for 95%, predominantly in 1.2 ns. The general CO rebinding properties are unexpectedly robust against changes in the interactions with close by aromatic residues Trp88 (G8) and Tyr36 (CD1). Molecular dynamics simulations of the CO complex suggest that interactions of the ligand with structural water molecules as well as its rotational freedom play a role in the high reactivity of the ligand and the heme. The slow exchange of ligands between heme and environment may result from a combination of hindered ligand access to the heme pocket by the network of distal aromatic residues, and low escape probability from the pocket.

Original languageEnglish (US)
Pages (from-to)10-16
Number of pages7
JournalChemical Physics
Volume396
Issue number1
DOIs
StatePublished - Mar 2 2012

Fingerprint

Truncated Hemoglobins
tuberculosis
hemoglobin
Heme
Ligands
ligands
Carbon Monoxide
escape
Photoexcitation
photoexcitation
Molecular dynamics
reactivity
interactions
Spectroscopy
molecular dynamics
Molecules
Water
Computer simulation

Keywords

  • Dynamics
  • Heme proteins
  • Truncated hemoglobin
  • Ultrafast spectroscopy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

Cite this

Ultrafast heme-ligand recombination in truncated hemoglobin HbO from Mycobacterium tuberculosis : A ligand cage. / Jasaitis, Audrius; Ouellet, Hugues; Lambry, Jean Christophe; Martin, Jean Louis; Friedman, Joel M.; Guertin, Michel; Vos, Marten H.

In: Chemical Physics, Vol. 396, No. 1, 02.03.2012, p. 10-16.

Research output: Contribution to journalArticle

Jasaitis, Audrius ; Ouellet, Hugues ; Lambry, Jean Christophe ; Martin, Jean Louis ; Friedman, Joel M. ; Guertin, Michel ; Vos, Marten H. / Ultrafast heme-ligand recombination in truncated hemoglobin HbO from Mycobacterium tuberculosis : A ligand cage. In: Chemical Physics. 2012 ; Vol. 396, No. 1. pp. 10-16.
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