PURIFICATION, CRYSTALLIZATION, AND PRELIMINARY-X-RAY STUDIES OF A BIFUNCTIONAL 5,10-METHENYL METHYLENE TETRAHYDROFOLATE CYCLOHYDROLASE/DEHYDROGENASE FROM ESCHERICHIA-COLI/

A bifunctional enzyme that catalyzes the conversion of formyltetrahydr ofolate to methylene-tetrahydrofolate (5,10-methenyltetrahydrofolate c yclohydrolase and 5,10-methylene tetrahydrofolate dehydrogenase), has been subcloned from a cDNA library, purified to homogeneity, and cryst allized. The crystals belong to space group I222, with unit cell dimen sions of a 64.5 Angstrom, b = 84.9 Angstrom, c = 146.1 Angstrom. The c rystal unit cell and diffraction is consistent with an asymmetric unit consisting of the enzyme monomer, and a specific volume of the unit c ell of 3.2 Angstrom(3)/Da. The crystals diffract to at least 2.8 Angst rom resolution after flash-cooling, when using a rotating anode x-ray source and an RAXIS image plate detector. A 2.56 Angstrom resolution n ative data set has been collected at beamline X12-C at the NSLS. (C) 1 997 Wiley-Liss, Inc.