DNA POLYMERASE II FROM ESCHERICHIA COLI. C.R.A. Muchmore, M.M. Blair, L. Shuvalova, M.F. Goodman, W.F. Anderson, Northwestern University Medical School, Department of Molecular Pharmacology and Biological Chemistry, Chicago, Illinois and University of Southern California, Department of Molecular Biology, Los Angeles, California.

Polymerase II from E. coli is a member of the group B ([[alpha]]-like) DNA polymerases as indicated by conserved sequence motifs. It contains both polymerase and 3'->5' exonuclease activity on a single polypeptide chain of 781 amino acid residues and is induced by DNA damage. The [[beta]][[gamma]] accessory protein complex of the polymerase III holoenzyme increases polymerase II processivity, raising questions about the nature of this interaction. Information about structure and function derived from the atomic structure of E. coli polymerase II may be applicable to other homologous group B polymerases like mammalian cellular DNA polymerase [[alpha]], eucaryotic viral polymerases and bacteriophage T4 polymerase.

Polymerase II crystallizes by sitting drop vapor diffusion with PEG 400 and citrate as precipitating agents at pH 5.8. Three heavy atom derivatives were produced under these conditions. Recently, the crystals have been successfully transferred to solutions of lower ionic strength and higher pH thus improving conditions for derivatizing crystals with heavy atom compounds.

X-ray diffraction data have been collected from the wild type polymerase II crystals at room temperature and at 103K from flash-frozen crystals. The crystals are of space group P21212 with one monomer per asymmetric unit. Initial phases for the wild type data were obtained by MIR methods. Phases were improved and extended to higher resolution by model building, phase combination and density modification techniques.

This work is supported by NIH GM48569, ES05355 and GM15075 .