Crystallization and crystallographic investigations of ribonucleotide reductase 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 carboxyl end of protein R2. Good quality crystals could only be obtained after improvement of the purification protocol and are of the space group R32 with hexagonal cell axes a = b = 226 A and c = 341 A. They contain 3 subunits per asymmetric unit and diffract to 2.5 A resolution in synchrotron radiation. A multiple isomorphous replacement map at 5.5A, improved by solvent flattening, shows that the dimeric molecules are elongated, about 110 A long. The 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 center.