... mecha-nism of transphosphorylation, which implies the ABFig. 3. Stereo diagram of the active center of HtA. (A) Superposition of the active-siteresidues of the 20 conformers of the solu-tion structure ... electrostatically with the othercharged groups. In the NMR structures, this sidechain of D40 is a short distance (£ 3A˚) from the sidechains of H42 and R95. Finally, the aromatic ring of F126, placed ... restraints used in the structure calculation, and type of distance restraints from NOEs.Restraints usedTotal distance restraints from NOEs 1988Total distance restraints from disulfide bonds...