Origin of the anomalous Fe-CO stretching mode in the CO complex of Ascaris hemoglobin

Tapan Kanti Das, Joel M. Friedman, Andrew P. Kloek, Daniel E. Goldberg, Denis L. Rousseau

Research output: Contribution to journalArticle

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Abstract

We report an unusually high frequency (543 cm-1) for an Fe-CO stretching mode in the CO complex of Ascaris suum hemoglobin as compared to vertebrate hemoglobins in which the frequency of the Fe-CO mode is much lower. A second Fe-CO stretching mode in Ascaris hemoglobin is observed at 515 cm-1. We propose that these two Fe-CO stretching modes arise from two protein conformers corresponding to interactions of the heme-bound CO with the B10-tyrosine or the E7-glutamine residues. This postulate is supported by spectra from the B10-Tyr → Phe mutant in which the 543 cm-1 line is absent. Thus, a strong polar interaction, such as hydrogen bonding, of the CO with the distal B 10 tyrosine residue is the dominant factor that causes this anomalously high frequency. Strong hydrogen bonding between O2 and distal residues in the oxy complex of Ascaris hemoglobin has been shown to result in a rigid structure, rendering an extremely low oxygen off rate [Gibson, Q. H., and Smith, M. H. (1965) Proc. R. Soc. London B 163, 206-214]. In contrast, the CO off rate in Ascaris hemoglobin is very similar to that in sperm whale myoglobin. The high CO off rate relative to that of O2 in Ascaris hemoglobin is attributed to a rapid equilibrium between the two conformations of the protein in the CO adduct, with the off rate being determined by the conformer with the higher rate.

Original languageEnglish (US)
Pages (from-to)837-842
Number of pages6
JournalBiochemistry
Volume39
Issue number4
DOIs
StatePublished - Feb 1 2000

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Carbon Monoxide
Stretching
Hydrogen Bonding
Tyrosine
Hydrogen bonds
Hemoglobins
Sperm Whale
Ascaris haemoglobin
Ascaris suum
Rigid structures
Protein Conformation
Myoglobin
Glutamine
Heme
Conformations
Vertebrates
Proteins
Oxygen

ASJC Scopus subject areas

  • Biochemistry

Cite this

Origin of the anomalous Fe-CO stretching mode in the CO complex of Ascaris hemoglobin. / Das, Tapan Kanti; Friedman, Joel M.; Kloek, Andrew P.; Goldberg, Daniel E.; Rousseau, Denis L.

In: Biochemistry, Vol. 39, No. 4, 01.02.2000, p. 837-842.

Research output: Contribution to journalArticle

Das, Tapan Kanti ; Friedman, Joel M. ; Kloek, Andrew P. ; Goldberg, Daniel E. ; Rousseau, Denis L. / Origin of the anomalous Fe-CO stretching mode in the CO complex of Ascaris hemoglobin. In: Biochemistry. 2000 ; Vol. 39, No. 4. pp. 837-842.
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