X-RAY CRYSTALLOGRAPHIC STUDIES OF RECOMBINANT INORGANIC PYROPHOSPHATASE FROM ESCHERICHIA-COLI

An E. coli inorganic pyrophosphatase overproducer and a method for a large-scale production of the homogeneous enzyme are described. The inorganic pyrophosphatase was crystallized in the form containing one subunit of a homohexameric molecule per asymmetric unit: space group R32, a = 110.4 Angstrom, c = 76.8 Angstrom. The electron density map to 2.5 Angstrom resolution phased with Eu- and Hg-derivatives (figure of merit, <m> = 0.51) was improved by the solvent flattening procedure (<m> = 0.77). The course of the polypeptide chain and the secondary structure elements, intersubunit contacts and positions of the active sites were characterized. Homology with S. cerevisiae inorganic pyrophosphatase structure was found.