title: Toward modeling H-NOX domains: a DFT study of heme-NO complexes as hydrogen bond acceptors.
abstract: Density functional theory calculations (PW91/STO-TZP, including basis-set superposition error corrections) have been used to evaluate hydrogen bond energies of five- and six-coordinate heme-NO complexes with phenol and imidazole, chosen as models for distal pocket tyrosine and histidine residues. The calculated interaction energies are approximately 2 kcal/mol for phenol and 3-4 kcal/mol for imidazole, which are 2-4 times smaller than the energies calculated for heme-O(2) complexes hydrogen-bonding with a distal histidine. Interestingly, the hydrogen bond energies are found to be very similar for five- and six-coordinate heme-NO complexes, which may be viewed as contrary to the interpretation of a recent observation on a bacterial H-NOX (Heme-Nitric oxide/OXygen-binding) protein with sequence homology to mammalian-soluble guanylate cyclase.
authors.affiliation: Department of Chemistry, University of Tromsø. Norway.
authors.forename: Espen
authors.initials: E
authors.lastname: Tangen
authors.forename: Anders
authors.initials: A
authors.lastname: Svadberg
authors.forename: Abhik
authors.initials: A
authors.lastname: Ghosh
mesh_terms: D000465:Algorithms; D001665:Binding Sites; D003198:Computer Simulation; D006418:Heme / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D009569:Nitric Oxide / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D009569:Nitric Oxide; D006418:Heme; D010100:Oxygen