A PRELIMINARY DESCRIPTION OF THE CRYSTAL-STRUCTURE OF GAMMA-GLUTAMYL-TRANSPEPTIDASE FROM ESCHERICHIA-COLI K-12

The structure of GGT [EC 2.3.2.2] from E. coli K-12 was studied at 3 A resolution by X-ray crystallography. Initial protein phases were calc ulated using two kinds of Pb2+ derivatives. The phases were refined by non-crystallographic a-fold symmetry electron density averaging combi ned with solvent flattening and histogram matching. The GGT molecule h as overall dimensions of 60 X 50 X 40 Angstrom. There are two antipara llel beta-pleated sheets consisting of 6 and beta-strands, The two bet a-sheets form a wall-like structure. Twelve short alpha-helices were d etected, of which the maximum length appears to be four helix turns.