ATOMIC-STRUCTURE OF THE RUVC RESOLVASE - A HOLLIDAY JUNCTION-SPECIFICENDONUCLEASE FROM ESCHERICHIA-COLI

The crystal structure of the RuvC protein, a Holliday junction resolva se from E. coli, has been determined at 2.5 Angstrom resolution. The e nzyme forms a dimer of 19 kDa subunits related by a dyad axis. Togethe r with results from extensive mutational analyses, the refined structu re reveals that the catalytic center, comprising four acidic residues, lies at the bottom of a cleft that nicely fits a DNA duplex. The stru ctural features of the dimer, with a 30 Angstrom spacing between the t wo catalytic centers, provide a substantially defined image of the Hol liday junction architecture. The folding topology in the vicinity of t he catalytic site exhibits a striking similarity to that of RNAase H1 from E. coil.