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Role of the distal hydrogen-bonding network in regulating oxygen affinity in the truncated hemoglobin III from Campylobacter jejuni

Posted November 16th, 2011 by xbarril
TitleRole of the distal hydrogen-bonding network in regulating oxygen affinity in the truncated hemoglobin III from Campylobacter jejuni
Publication TypeJournal Article
Year of Publication2011
AuthorsManez, AP, Lu C, Boechi L, Marti MA, Shepherd M, Wilson JL, Poole RK, Luque FJ, Yeh SR, Estrin DA
JournalBiochemistry
Volume50
Issue19
Pagination3946 - 3956
Date Published2011/05/17/
KeywordsBacterial Proteins/chemistry/genetics; Campylobacter jejuni/chemistry/genetics; Glycine/genetics; Heme/chemistry/genetics; Histidine/chemistry/genetics; Hydrogen Bonding; Ligands; Molecular Dynamics Simulation; Mutagenesis, Raman; Truncated Hemoglobins/chemistry/genetics; Tryptophan/chemistry/genetics; Tyrosine/chemistry/genetics, Site-Directed; Oxygen/chemistry/metabolism; Protein Binding/genetics; Spectrum Analysis
AbstractOxygen 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.