The structure of the ADP complex of the enzyme 3-phosphoglycerate kinase (PGK, E.C. 2.7.2.3) from Bacillus stearothermophilus NCA-1503 has been determined by the method of molecular replacement. The structure has been refined to an R factor of 0.16 for all data between 10.0 and 1.65A resolution, using data collected on the Hendrix-Lentfer imaging plate at the EMBL outstation in Hamburg. The r.m.s, deviations from stereochemical ideality are 0.010 and 0.011 A for bonds and planes, respectively. Although crystallized in the presence of the nucleotide product MgATP, the highresolution structure reveals the bound 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 ° closer together than is found in the yeast and horse-muscle apo-enzyme structures, this structure represents the 'open' rather than the 'closed', catalytically competent form, of the enzyme.

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The trypsin from Fusarium oxysporum is equally homologous to trypsins from Streptomyces griseus, Streptomyces erythraeus and to bovine trypsin. A DFP (diisopropylfluorophosphate) inhibited form of the enzyme has been crystallized from 1.4 M Na2SO4, buffered with citrate at pH 5.0-5.5. The crystals belong to space group P2(1) with cell parameters a = 33.43 A, b = 67.65 A, c = 39.85 A and beta = 107.6 degrees. There is one protein molecule in the asymmetric unit. X-ray diffraction data to a resolution of 1.8 A were collected on film using synchrotron radiation. The structure was solved by molecular replacement using models of bovine and S. griseus trypsins and refined to an R-factor of 0.141. The overall fold is similar to other trypsins, with some insertions and deletions. There is no evidence of the divalent cation binding sites seen in other trypsins. The covalently bound inhibitor molecule is clearly visible.