Solution structure of the histidine-containing phosphocarrier protein fromStaphylococcus carnosus

The solution structure of histidine-containing phosphocarrier protein from Staphylococcus carnosus was determined by two- and three-dimensional nuclea r magnetic resonance (NMR) spectroscopy on uniformly N-15-enriched protein. The main structural element is an antiparallel beta-pleated sheet with fou r strands At B, C, and D arranged with the topology A-D-B-C. Strand A compr ises residues 2 to 8, strand B residues 32 to 37, strand C reidues 40 to 43 , and strand D residues 59 to 66. Three right-handed helices are arranged o n top of the beta-pleated sheet. Helix a reaches from residue 16 to 29, hel ix b from residue 48 to 53, and helix c from residue 72 to 53. Strands B an d C of the beta-pleated sheet are connected by a type II' turn. The hydroxy l proton of Ser-31 is exchanging with the solvent so slowly that cross peak s can be detected in two-dimensional NMR spectra based on homonuclear J-cou plings. The imidazole ring of the active-center His-15, which is partly cha rged in the structure determined at pH 7.2, is located above the N-terminal end of helix a, perpendicular to its axis. The N-delta 1 atom of His-15, a ccepting the phosphoryl from enzyme I, is exposed to the solvent.