Ligand binding in the ferric and ferrous states of Paramecium hemoglobin

T. K. Das, R. E. Weber, S. Dewilde, J. B. Wittenberg, B. A. Wittenberg, K. Yamauchi, M. L. Van Hauwaert, L. Moens, Denis L. Rousseau

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Abstract

The unicellular protozoan Paramecium caudatum contains a monomeric hemoglobin (Hb) that has only 116 amino acid residues. This Hb shares the simultaneous presence of a distal E7 glutamine and a B10 tyrosine with several invertebrate Hbs. In the study presented here, we have used ligand binding kinetics and resonance Raman spectroscopy to characterize the effect of the distal pocket residues of Paramecium Hb in stabilizing the heme-bound ligands. In the ferric state, the high-spin to low-spin (aquohydroxy) transition takes place with a pK(a) of ~9.0. The oxygen affinity (P50 = 0.45 Torr) is similar to that of myoglobin. The oxygen on- and off-rates are also similar to those of sperm whale myoglobin. Resonance Raman data suggest hydrogen bonding stabilization of bound oxygen, evidenced by a relatively low frequency of Fe-OO stretching (563 cm-1). We propose that the oxy complex is an equilibrium mixture of a hydrogen-bonded closed structure and an open structure. Oxygen will dissociate preferentially from the open structure, and therefore, the fraction of open structure population controls the rate of oxygen dissociation. In the CO complex, the Fe-CO stretching frequency at 493 cm-1 suggests an open heme pocket, which is consistent with the higher on- and off-rates for CO relative to those in myoglobin. A high rate of ligand binding is also consistent with the observation of an Fe-histidine stretching frequency at 220 cm-1, indicating the absence of significant proximal strain. We postulate that the function of Paramecium Hb is to supply oxygen for cellular oxidative processes.

Original languageEnglish (US)
Pages (from-to)14330-14340
Number of pages11
JournalBiochemistry
Volume39
Issue number46
DOIs
StatePublished - Nov 21 2000

Fingerprint

Paramecium
Hemoglobins
Myoglobin
Oxygen
Ligands
Carbon Monoxide
Stretching
Heme
Paramecium caudatum
Oxygen supply
Sperm Whale
Glutamine
Population Control
Histidine
Raman Spectrum Analysis
Tyrosine
Invertebrates
Hydrogen Bonding
Raman spectroscopy
Hydrogen

ASJC Scopus subject areas

  • Biochemistry

Cite this

Das, T. K., Weber, R. E., Dewilde, S., Wittenberg, J. B., Wittenberg, B. A., Yamauchi, K., ... Rousseau, D. L. (2000). Ligand binding in the ferric and ferrous states of Paramecium hemoglobin. Biochemistry, 39(46), 14330-14340. https://doi.org/10.1021/bi001681d

Ligand binding in the ferric and ferrous states of Paramecium hemoglobin. / Das, T. K.; Weber, R. E.; Dewilde, S.; Wittenberg, J. B.; Wittenberg, B. A.; Yamauchi, K.; Van Hauwaert, M. L.; Moens, L.; Rousseau, Denis L.

In: Biochemistry, Vol. 39, No. 46, 21.11.2000, p. 14330-14340.

Research output: Contribution to journalArticle

Das, TK, Weber, RE, Dewilde, S, Wittenberg, JB, Wittenberg, BA, Yamauchi, K, Van Hauwaert, ML, Moens, L & Rousseau, DL 2000, 'Ligand binding in the ferric and ferrous states of Paramecium hemoglobin', Biochemistry, vol. 39, no. 46, pp. 14330-14340. https://doi.org/10.1021/bi001681d
Das TK, Weber RE, Dewilde S, Wittenberg JB, Wittenberg BA, Yamauchi K et al. Ligand binding in the ferric and ferrous states of Paramecium hemoglobin. Biochemistry. 2000 Nov 21;39(46):14330-14340. https://doi.org/10.1021/bi001681d
Das, T. K. ; Weber, R. E. ; Dewilde, S. ; Wittenberg, J. B. ; Wittenberg, B. A. ; Yamauchi, K. ; Van Hauwaert, M. L. ; Moens, L. ; Rousseau, Denis L. / Ligand binding in the ferric and ferrous states of Paramecium hemoglobin. In: Biochemistry. 2000 ; Vol. 39, No. 46. pp. 14330-14340.
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AU - Das, T. K.

AU - Weber, R. E.

AU - Dewilde, S.

AU - Wittenberg, J. B.

AU - Wittenberg, B. A.

AU - Yamauchi, K.

AU - Van Hauwaert, M. L.

AU - Moens, L.

AU - Rousseau, Denis L.

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