Structure and reactivity of hexacoordinate hemoglobins

Smita Kakar, Federico G. Hoffman, Jay F. Storz, Marian Fabian, Mark S. Hargrove

Research output: Contribution to journalReview articlepeer-review

127 Scopus citations


The heme prosthetic group in hemoglobins is most often attached to the globin through coordination of either one or two histidine side chains. Those proteins with one histidine coordinating the heme iron are called "pentacoordinate" hemoglobins, a group represented by red blood cell hemoglobin and most other oxygen transporters. Those with two histidines are called "hexacoordinate hemoglobins", which have broad representation among eukaryotes. Coordination of the second histidine in hexacoordinate Hbs is reversible, allowing for binding of exogenous ligands like oxygen, carbon monoxide, and nitric oxide. Research over the past several years has produced a fairly detailed picture of the structure and biochemistry of hexacoordinate hemoglobins from several species including neuroglobin and cytoglobin in animals, and the nonsymbiotic hemoglobins in plants. However, a clear understanding of the physiological functions of these proteins remains an elusive goal.

Original languageEnglish (US)
Pages (from-to)1-14
Number of pages14
JournalBiophysical Chemistry
Issue number1-3
StatePublished - Nov 2010
Externally publishedYes


  • Evolution
  • Hexacoordinate hemoglobin
  • Kinetics
  • Ligand binding
  • Neuroglobin
  • Plant hemoglobin
  • Structure

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Organic Chemistry


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