title: Role of the distal hydrogen-bonding network in regulating oxygen affinity in the truncated hemoglobin III from Campylobacter jejuni.
abstract: Oxygen affinity in heme-containing proteins is determined by a number of factors, such as the nature and conformation of the distal residues that stabilize the heme bound-oxygen via hydrogen-bonding interactions. The truncated hemoglobin III from Campylobacter jejuni (Ctb) contains three potential hydrogen-bond donors in the distal site: TyrB10, TrpG8, and HisE7. Previous studies suggested that Ctb exhibits an extremely slow oxygen dissociation rate due to an interlaced hydrogen-bonding network involving the three distal residues. Here we have studied the structural and kinetic properties of the G8(WF) mutant of Ctb and employed state-of-the-art computer simulation methods to investigate the properties of the O(2) adduct of the G8(WF) mutant, with respect to those of the wild-type protein and the previously studied E7(HL) and/or B10(YF) mutants. Our data indicate that the unique oxygen binding properties of Ctb are determined by the interplay of hydrogen-bonding interactions between the heme-bound ligand and the surrounding TyrB10, TrpG8, and HisE7 residues.
authors.affiliation: Departamento de Química Inorgánica, Analítica, y Química Fisica, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Ciudad Universitaria , Buenos Aires, Argentina.
authors.forename: Pau
authors.initials: P
authors.lastname: Arroyo Mañez
authors.forename: Changyuan
authors.initials: C
authors.lastname: Lu
authors.forename: Leonardo
authors.initials: L
authors.lastname: Boechi
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Martí
authors.forename: Mark
authors.initials: M
authors.lastname: Shepherd
authors.forename: Jayne Louise
authors.initials: JL
authors.lastname: Wilson
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Luque
authors.forename: Syun-Ru
authors.initials: SR
authors.lastname: Yeh
authors.forename: Darío A
authors.initials: DA
authors.lastname: Estrin
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D016123:Campylobacter jejuni / Q000737:chemistry* / Q000235:genetics; D005998:Glycine / Q000235:genetics; D006418:Heme / Q000737:chemistry / Q000235:genetics; D006639:Histidine / Q000737:chemistry / Q000235:genetics; D006860:Hydrogen Bonding; D008024:Ligands; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D013059:Spectrum Analysis, Raman; D054793:Truncated Hemoglobins / Q000737:chemistry* / Q000235:genetics; D014364:Tryptophan / Q000737:chemistry / Q000235:genetics; D014443:Tyrosine / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D054793:Truncated Hemoglobins; D014443:Tyrosine; D006418:Heme; D006639:Histidine; D014364:Tryptophan; D010100:Oxygen; D005998:Glycine