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

ARROYO MAÑEZ, P.; LU, C.; BOECHI, L.; MARTI, M.A.; SHEPHERD, M.; WILSON, J.L.; POOLE, R.K.; LUQUE, F.J.; YEH, S.R.; ESTRIN, D.A.

BIOCHEMISTRY

AMER CHEMICAL SOC

Año: 2011 vol. 50 p. 3946 - 3956

0006-2960

Oxygen affinity in heme-containing proteins is determinedby a number of factors, such as the nature and conformation of the distalresidues that stabilize the heme bound-oxygen via hydrogen-bondinginteractions. 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 exhibitsan extremely slow oxygen dissociation rate due to an interlaced hydrogen-bonding network involving the three distal residues. Here we have studiedthe structural and kinetic properties of the G8WF mutant of Ctb andemployed state-of-the-art computer simulation methods to investigate theproperties of the O2 adduct of the G8WF mutant, with respect to those ofthe wild-type protein and the previously studied E7HL and/or B10YFmutants. Our data indicate that the unique oxygen binding properties ofCtb are determined by the interplay of hydrogen-bonding interactions between the heme-bound ligand and the surroundingTyrB10, TrpG8, and HisE7 residues.