CRYSTAL-STRUCTURE OF CYTOPLASMIC ESCHERICHIA-COLI PEPTIDYL-PROLYL ISOMERASE - EVIDENCE FOR DECREASED MOBILITY OF LOOPS UPON COMPLEXATION

The structure of the unliganded form of the Escherichia coil cytoplasm ic peptidyl-prolyl isomerase (ppiB gene product) in a new crystal form was determined by the molecular replacement method and refined to an R-factor of 16.1% at 2.1 Angstrom resolution. The enzyme crystallized in the orthorhombic C222(1) space group with unit cell dimensions of a = 44.7 Angstrom, b = 68.2 Angstrom and c = 102.0 Angstrom. Comparison with the reported structure of the enzyme complexed with the tripepti de substrate succinyl-Ala-Pro-Ala-p-nitroanilide revealed subtle chang es that occur upon complex formation. There is evidence to suggest tha t two surface loops have significantly reduced mobility in the complex ed structure. (C) Academic Press Limited.