title: The binding of carbon monoxide and nitric oxide to leghaemoglobin in comparison with other haemoglobins.
abstract: Haemoglobins have the ability to discriminate between oxygen and other diatomic molecules. To further understanding of this process the X-ray crystal structures of carbonmonoxy and nitrosyl-leghaemoglobin have been determined at 1.8 A resolution. The ligand geometry is discussed in detail and the controversial issue of bent versus linear carbon monoxide binding is addressed. The bond angle of 160 degrees for CO-leghaemoglobin is in conflict with recent spectroscopy results on myoglobin but is consistent with angles obtained for myoglobin X-ray crystal structures. In contrast to the numerous carbon monoxide studies, very little stereochemical information is available for the nitric oxide adduct of haemoglobin. This is provided by the X-ray structure of NO-leghaemoglobin, which conforms to expected geometry with an Fe-NO angle of 147 degrees and a lengthened iron-proximal histidine bond. Thus crystallographic evidence is given for the predicted weakening of this bond on the binding of nitric oxide.
authors.affiliation: Institute of Crystallography, Russian Academy of Sciences, Moscow, Russia.
authors.forename: E H
authors.initials: EH
authors.lastname: Harutyunyan
authors.forename: T N
authors.initials: TN
authors.lastname: Safonova
authors.forename: I P
authors.initials: IP
authors.lastname: Kuranova
authors.forename: A N
authors.initials: AN
authors.lastname: Popov
authors.forename: A V
authors.initials: AV
authors.lastname: Teplyakov
authors.forename: G V
authors.initials: GV
authors.lastname: Obmolova
authors.forename: B K
authors.initials: BK
authors.lastname: Valnshtein
authors.forename: G G
authors.initials: GG
authors.lastname: Dodson
authors.forename: J C
authors.initials: JC
authors.lastname: Wilson
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007887:Fabaceae / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D007874:Leghemoglobin / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D010946:Plants, Medicinal; D011485:Protein Binding; D017433:Protein Structure, Secondary
chemical_list: D007874:Leghemoglobin; D008024:Ligands; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide