Keywords: Bacterium, Cold Adaptation, Fish, Hemoglobin, Hexacoordination, Neuroglobin, Bacteria (microorganisms), Bis-Histidine, Protein Data Bank, Structural Analyses,
Affiliations: *** IBB - CNR ***
Institute of Protein Biochemistry, CNR, Via Pietro Castellino 111, I-80131 Naples, Italy
Department of Chemistry, University of Naples Federico II, Complesso Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy
Institute of Biostructures and Bioimages, CNR, Via Mezzocannone 16, I-80134 Naples, Italy
References: Not available.
Hemoproteins in the cold
The properties of hemoproteins strictly depend on the type and orientation of axial ligands. Here, the orientations of axially coordinated His in bis-His complexes and the heme geometry in protein data bank have been analyzed. The effect of the bis-histidyl formation on the heme cavity of Antarctic fish hemoglobins has been also evaluated. The results show that protein matrix exerts a major effect on the conformation of axially ligated histidines: the imidazoles in bis-His complexes occupy a preferred relative orientation in globins and in model systems, whereas they adopt a variety of relative orientations in other hemoproteins. The bis-histidyl adducts affect the heme geometry inducing larger distortions from planarity with respect to other ligands. These deviations are larger in bis-His multiheme cytochromes than in globins. In Antarctic fish hemoglobins the bis-histidyl adduct adopts preferentially a distorted coordination and the formation of the bis-His complex induces a slight but significant modification in the shape, area and volume of the heme cavity. (C) 2009 Elsevier B.V. All rights reserved.