NMR Studies of Monoliganded Fe-Co Hybrid Hemoglobins: Their Quaternary Structure and Proximal Histidine Coordination

Toshiro Inubushi, Cynthia D’Ambrosio, Masao Ikeda-Saito, Takashi Yonetani

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Tricobalt-substituted Fe-Co hybrid hemoglobins have been synthesized by cross-linking symmetric Fe-Co hybrid HbA and Co-substituted mutant HbC (β6 Glu-Lys) with bis(3, 5-dibromosalicyl) fumarate. Carbon monoxy derivatives of these molecules can serve as important models of monoliganded hemoglobins, the intermediate species produced in the First step of oxygen binding to hemoglobin. Acceptance of the first ligand in an a subunit gave essentially no change in the proximal histidine coordination in the remaining deoxy subunits and a small alteration of deoxy quaternary structure. However, when the first ligand was bound to a 0 subunit, significant change in the proximal histidine coordination and complete elimination of one hydrogen bond in the deoxy quaternary structure occurred. Such substantial differences in the structures of the two monoliganded hemoglobins obtained by NMR allow us to postulate the possible course of oxygen binding. Also, the observation of asynchronous decreases in the intensities of so-called “T-state” markers and the absence of concomitant increases in the so-called ”R-state” marker indicate the existence of more than two quaternary structures for Hb and contradict the two-state allosteric theory.

Original languageEnglish
Pages (from-to)3799-3803
Number of pages5
JournalJournal of the American Chemical Society
Volume108
Issue number13
DOIs
Publication statusPublished - 1986 Jan 1

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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