CRYSTALLIZATION AND CRYSTALLOGRAPHIC INVESTIGATIONS OF RIBONUCLEOTIDEREDUCTASE PROTEIN R1 FROM ESCHERICHIA-COLI

Crystals of Escherichia coli ribonucleotide reductase protein R1 have been grown in complex with a synthetic peptide corresponding to the ca rboxyl end of protein R2. Good quality crystals could only be obtained after improvement of the purification protocol and are of the space g roup R32 with hexagonal cell axes a = b = 226 Angstrom and c = 341 Ang strom. They contain 3 subunits per asymmetric unit and diffract to 2.5 Angstrom resolution in synchrotron radiation. A multiple isomorphous replacement map. at 5.5 Angstrom, improved by solvent flattening, show s that the dimeric molecules are elongated, about 110 Angstrom long. T he dimer is thin in the middle around the molecular two-fold axis. The subunit is shaped like a bowl, probably with the active site in its c enter.