Title
Structural bases for heme binding and diatomic ligand recognition in truncated hemoglobins Structural bases for heme binding and diatomic ligand recognition in truncated hemoglobins
Author
Faculty/Department
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences . Biomedical Sciences
Publication type
article
Publication
New York, N.Y. ,
Subject
Biology
Human medicine
Source (journal)
Journal of inorganic biochemistry. - New York, N.Y.
Volume/pages
99(2005) :1 , p. 97-109
ISSN
0162-0134
ISI
000226555000009
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
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 2040 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 á-helical sandwich, which represents a striking editing of the highly conserved 3-on-3 á-helical globin fold, achieved through deletion/truncation of á-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.
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