STRUCTURE OF THE ADP COMPLEX OF THE 3-PHOSPHOGLYCERATE KINASE FROM BACILLUS-STEAROTHERMOPHILUS AT 1.65 ANGSTROM

The structure of the ADP complex of the enzyme 3-phosphoglycerate kina se (PGK, E.C.2.7.2.3), from Bacillus stearothermophilus NCA-1503 has b een determined by the method of molecular replacement. The structure h as been refined to an R factor of 0.16 for all data between 10.0 and 1 .65 angstrom resolution, using data collected on the Hendrix-Lentfer i maging plate at the EMBL outstation in Hamburg. The r.m.s. deviations from stereochemical ideality are 0.010 and 0.011 angstrom for bonds an d planes, respectively. Although crystallized in the presence of the n ucleotide product MgATP, the high-resolution structure reveals the bou nd nucleotide to be MgADP reflecting the low intrinsic ATPase activity of PGK. Although the two domains of this enzyme are found to be some 4.5-degrees closer together than is found in the yeast and horse-muscl e apo-enzyme structures, this structure represents the 'open' rather t han the 'closed', catalytically competent form, of the enzyme.