Effect of phosphorylation on hydrogen-bonding interactions of the active site histidine of the phosphocarrier protein HPr of the phosphoenolpyruvate-dependent phosphotransferase system determined by 15N NMR spectroscopy.
The phosphocarrier protein HPr of the phosphoenolpyruvate-dependent sugar transport system of Escherichia coli can exist in a phosphorylated and a nonphosphorylated form. During phosphorylation, the phosphoryl group is carried on a histidine residue, His15. The hydrogen-bonding state of this histidine was examined with 15N NMR. For this purpose we selectively enriched the histidine imidazole nitrogens with 15N by supplying an E. coli histidine auxotroph with the amino acid labeled either at the N delta 1 and N epsilon 2 positions or at only the N delta 1 position. 15N NMR spectra of two synthesized model compounds, phosphoimidazole and phosphomethylimidazole, were also recorded. We show that, prior to phosphorylation, the protonated His15 N epsilon 2 is strongly hydrogen bonded, most probably to a carboxylate moiety. The H-bond should strengthen the nucleophilic character of the deprotonated N delta 1, resulting in a good acceptor for the phosphoryl group. The hydrogen bond to the His15 N delta 1 breaks upon phosphorylation of the residue. Implications of the H-bond structure for the mechanism of phosphorylation of HPr are discussed.
van Dijk
A A
AA
Department of Physical Chemistry, State University of Groningen, The Netherlands.
de Lange
L C
LC
Bachovchin
W W
WW
Robillard
G T
GT
D001426:Bacterial Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology; D006639:Histidine; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational
D001426:Bacterial Proteins; D006639:Histidine; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr