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Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction.
Biochemistry 1996; 35(24):8068-74B

Abstract

The homodimeric hemoglobin from the mollusk Scapharca inaequivalvis (HbI) yields very stable ferrous and ferric cyanide adducts. The stability of the ferrous complex is particularly unusual such that it enabled determination of the spectroscopic properties of the complex and the characterization of the cyanide binding reaction to deoxygenated HbI at equilibrium and kinetically. The absorption spectrum of the ferrous cyanide complex is typical of a low-spin derivative; in the near-infrared region, it displays two bands at 695 and 840 nm attributable to charge transfer transitions. At pH 9.2, cyanide binds to deoxy HbI with no cooperativity and an apparent affinity constant of 17 M-1, which is about 10-fold higher than that for deoxy horse heart myoglobin. The rate of cyanide dissociation from both the ferrous and the ferric HbI adducts is slow relative to those of the other hemoproteins investigated to date and provides the major contribution to the unusual affinity for the ligand. The rate of cyanide binding to the ferric protein, in which the pentacoordinate derivative is the dominant species, is about 100-fold faster relative to that of the ferrous protein. In structural terms, the high affinity for cyanide of Scapharca hemoglobin has been ascribed to the decreased overall polarity of the heme pocket which is related to the localization of the heme groups at the subunit interface.

Authors+Show Affiliations

Department of Biochemical Sciences A. Rossi Fanelli, University La Sapienza, Rome, Italy.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

8672511

Citation

Boffi, A, et al. "Unusual Affinity of Cyanide for Ferrous and Ferric Scapharca Inaequivalvis Homodimeric Hemoglobin. Equilibria and Kinetics of the Reaction." Biochemistry, vol. 35, no. 24, 1996, pp. 8068-74.
Boffi A, Ilari A, Spagnuolo C, et al. Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction. Biochemistry. 1996;35(24):8068-74.
Boffi, A., Ilari, A., Spagnuolo, C., & Chiancone, E. (1996). Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction. Biochemistry, 35(24), pp. 8068-74.
Boffi A, et al. Unusual Affinity of Cyanide for Ferrous and Ferric Scapharca Inaequivalvis Homodimeric Hemoglobin. Equilibria and Kinetics of the Reaction. Biochemistry. 1996 Jun 18;35(24):8068-74. PubMed PMID: 8672511.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction. AU - Boffi,A, AU - Ilari,A, AU - Spagnuolo,C, AU - Chiancone,E, PY - 1996/6/18/pubmed PY - 1996/6/18/medline PY - 1996/6/18/entrez SP - 8068 EP - 74 JF - Biochemistry JO - Biochemistry VL - 35 IS - 24 N2 - The homodimeric hemoglobin from the mollusk Scapharca inaequivalvis (HbI) yields very stable ferrous and ferric cyanide adducts. The stability of the ferrous complex is particularly unusual such that it enabled determination of the spectroscopic properties of the complex and the characterization of the cyanide binding reaction to deoxygenated HbI at equilibrium and kinetically. The absorption spectrum of the ferrous cyanide complex is typical of a low-spin derivative; in the near-infrared region, it displays two bands at 695 and 840 nm attributable to charge transfer transitions. At pH 9.2, cyanide binds to deoxy HbI with no cooperativity and an apparent affinity constant of 17 M-1, which is about 10-fold higher than that for deoxy horse heart myoglobin. The rate of cyanide dissociation from both the ferrous and the ferric HbI adducts is slow relative to those of the other hemoproteins investigated to date and provides the major contribution to the unusual affinity for the ligand. The rate of cyanide binding to the ferric protein, in which the pentacoordinate derivative is the dominant species, is about 100-fold faster relative to that of the ferrous protein. In structural terms, the high affinity for cyanide of Scapharca hemoglobin has been ascribed to the decreased overall polarity of the heme pocket which is related to the localization of the heme groups at the subunit interface. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/8672511/Unusual_affinity_of_cyanide_for_ferrous_and_ferric_Scapharca_inaequivalvis_homodimeric_hemoglobin._Equilibria_and_kinetics_of_the_reaction L2 - https://dx.doi.org/10.1021/bi9601971 DB - PRIME DP - Unbound Medicine ER -