Phosphorylation on histidine is accompanied by localized structural changes in the phosphocarrier protein, HPr from Bacillus subtilis

The histidine-containing protein (HPr) of bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) serves a central role in a series of phosphotransfer reactions used for the translocation of sugars across cell membranes. These studies report the high-definition solution structures of both the unphosphorylated and histidine phosphorylated (P-His) forms of HPr from Bacillus subtilis. Consistent with previous NMR studies, local conformational adjustments occur upon phosphorylation of His 15, which positions the phosphate group to serve as a hydrogen bond acceptor for the amide protons of Ala 16 and Arg 17 and to interact favorably with the alpha-helix macrodipole. However, the positively charged side chain of the highly conserved Arg 17 does not appear to interact directly with phospho-His 15, suggesting that Arg 17 plays a role in the recognition of other PTS enzymes or in phosphotransfer reactions directly. Unlike the results reported for Escherichia coli P-His HPr (Van Nuland NA, Boelens R, Scheek RM, Robillard GT, 1995, J Mol Biol 246: 180-193), our data indicate that phosphorylation of His 15 is not accompanied by adoption of unfavorable backbone conformations for active site residues in B. subtilis P-Ser HPr.