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Asymmetric hemoglobin hybrids.
J Mol Biol 1996; 263(1):90-7JM

Abstract

We have investigated the functional properties of hemoglobin (Hb) valency hybrids, and specifically whether it makes a difference if the oxidized subunits are on the same dimer (asymmetric hybrid) or not. CO recombination kinetics were used to probe the allosteric equilibrium of tetramers with two oxidized subunits. Asymmetric hybrids were prepared by mixing HbCO with a large excess of cyano-metHb; dimer exchange occurs in the order of seconds, producing a population of fully liganded [dimer-CO/dimer-CN] hybrids; these hybrids could then be photolysed to study CO rebinding to the doubly liganded [dimer-deoxy/dimer-CN] species. Before mixing, the HbCO samples typically show 30 to 50% slow phase, characteristic of deoxy (or T-state) Hb. Addition of HbCN to these samples decreased the slow fraction. The higher the ratio of HbCN to HbCO, the less slow phase was observed, with about 5% slow phase at a ratio of 10:1. This would indicate that the photoproduct [deoxy-dimer/ dimer-CN] is not predominantly in the low-affinity (T-state) conformation. We did not observe the difference between asymmetric and symmetric hybrids expected from published studies. The difference between the present flash photolysis results and the published equilibrium studies could be due to a kinetic factor: if the conversion to the T-state is slow after photolysis, then the biomolecular kinetics will reflect the pre-flash conditions of fully liganded (R-state) hemoglobin.

Authors+Show Affiliations

INSERM U299, Hôpital de Bicêtre, Le Kremlin Bicêtre, France.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

8890915

Citation

Marden, M C., et al. "Asymmetric Hemoglobin Hybrids." Journal of Molecular Biology, vol. 263, no. 1, 1996, pp. 90-7.
Marden MC, Griffon N, Poyart C. Asymmetric hemoglobin hybrids. J Mol Biol. 1996;263(1):90-7.
Marden, M. C., Griffon, N., & Poyart, C. (1996). Asymmetric hemoglobin hybrids. Journal of Molecular Biology, 263(1), pp. 90-7.
Marden MC, Griffon N, Poyart C. Asymmetric Hemoglobin Hybrids. J Mol Biol. 1996 Oct 18;263(1):90-7. PubMed PMID: 8890915.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Asymmetric hemoglobin hybrids. AU - Marden,M C, AU - Griffon,N, AU - Poyart,C, PY - 1996/10/18/pubmed PY - 1996/10/18/medline PY - 1996/10/18/entrez SP - 90 EP - 7 JF - Journal of molecular biology JO - J. Mol. Biol. VL - 263 IS - 1 N2 - We have investigated the functional properties of hemoglobin (Hb) valency hybrids, and specifically whether it makes a difference if the oxidized subunits are on the same dimer (asymmetric hybrid) or not. CO recombination kinetics were used to probe the allosteric equilibrium of tetramers with two oxidized subunits. Asymmetric hybrids were prepared by mixing HbCO with a large excess of cyano-metHb; dimer exchange occurs in the order of seconds, producing a population of fully liganded [dimer-CO/dimer-CN] hybrids; these hybrids could then be photolysed to study CO rebinding to the doubly liganded [dimer-deoxy/dimer-CN] species. Before mixing, the HbCO samples typically show 30 to 50% slow phase, characteristic of deoxy (or T-state) Hb. Addition of HbCN to these samples decreased the slow fraction. The higher the ratio of HbCN to HbCO, the less slow phase was observed, with about 5% slow phase at a ratio of 10:1. This would indicate that the photoproduct [deoxy-dimer/ dimer-CN] is not predominantly in the low-affinity (T-state) conformation. We did not observe the difference between asymmetric and symmetric hybrids expected from published studies. The difference between the present flash photolysis results and the published equilibrium studies could be due to a kinetic factor: if the conversion to the T-state is slow after photolysis, then the biomolecular kinetics will reflect the pre-flash conditions of fully liganded (R-state) hemoglobin. SN - 0022-2836 UR - https://www.unboundmedicine.com/medline/citation/8890915/Asymmetric_hemoglobin_hybrids L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-2836(96)90558-6 DB - PRIME DP - Unbound Medicine ER -