Journal
IUBMB LIFE
Volume 65, Issue 2, Pages 121-126Publisher
WILEY-BLACKWELL
DOI: 10.1002/iub.1121
Keywords
human hemoglobin; proximal heme side; distal heme side; ligand discrimination; a- and ss-chain nonequivalence; transient ligand-binding properties
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Funding
- National Institute of Biostructures and Biosystems (INBB) of Italy
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The Summary: Ligand binding to the heme distal side is a paradigm of biochemistry. However, X-ray crystallographic studies highlighted the possibility that O2 and NO2- may bind to the proximal heme side of ferrous human hemoglobin (Hb) alpha-chains complexed with the alpha-hemoglobin stabilizing protein and to ferric human hemoglobin beta-chains, respectively. Strikingly, the role generally played by the proximal HisF8 residue is played by the distal HisE7 side chain forming the trans axial ligand of the hemeFe atom. This: i) brings to light that Hb may utilize both heme distal and proximal sides for ligand discrimination, ii) draws attention to the nonequivalence of alpha- and beta-chains, and iii) highlights the possibility that partially unfolded Hb derivatives may display transient ligand-binding properties different from those of the native globin. (c) 2013 IUBMB Life, 65(2)121126, 2013
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