Structural bases for heme binding and diatomic ligand recognition in truncated hemoglobins

Mario Milani, Alessandra Pesce, Marco Nardini, Hugues Ouellet, Yannick Ouellet, Sylvia Dewilde, Alessio Bocedi, Paolo Ascenzi, Michel Guertin, Luc Moens, Joel M. Friedman, Jonathan B. Wittenberg, Martino Bolognesi

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


Truncated hemoglobins (trHbs) are low-molecular-weight oxygen-binding heme-proteins distributed in eubacteria, cyanobacteria, unicellular eukaryotes, and in higher plants, constituting a distinct group within the hemoglobin (Hb) superfamily. TrHbs display amino acid sequences 20-40 residues shorter than classical (non)vertebrate Hbs and myoglobins, to which they are scarcely related by sequence similarity. The trHb tertiary structure is based on a 2-on-2 α-helical sandwich, which represents a striking editing of the highly conserved 3-on-3 α-helical globin fold, achieved through deletion/truncation of α-helices and specific residue substitutions. Despite their 'minimal' polypeptide chain span, trHbs display an inner tunnel/cavity system held to support ligand diffusion to/from the heme distal pocket, accumulation of heme ligands within the protein matrix, and/or multiligand reactions. Moreover, trHbs bind and effectively stabilize the heme and recognize diatomic ligands (i.e., O2, CO, NO, and cyanide), albeit with varying thermodynamic and kinetic parameters. Here, structural bases for heme binding and diatomic ligand recognition by trHbs are reviewed.

Original languageEnglish (US)
Pages (from-to)97-109
Number of pages13
JournalJournal of Inorganic Biochemistry
Issue number1
StatePublished - Jan 2005


  • Diatomic ligand recognition
  • Heme stabilization
  • Hemoglobin
  • Myoglobin
  • Protein cavities
  • Truncated hemoglobin

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry


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