Role of the Distal Hydrogen-Bonding Network in Regulating Oxygen Affinity in the Truncated Hemoglobin III from Campylobacter jejuni

ARROYO MAÑEZ P, CHANGUAN L, BOECHI L, MARTI MA, SHEPHERD M, WILSON J, POOLE R, LUQUE J, YEH SR, AND ESTRIN DA

BIOCHEMISTRY

AMER CHEMICAL SOC

Año: 2011 vol. 50 p. 3946 - 3956

0006-2960

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 G8WF mutant of Ctb and employed state-of-the-art computer simulation methods to investigate the properties of the O2 adduct of the G8WF mutant, with respect to those of the wild-type protein and the previously studied E7HL and/or B10YF 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.