Catherine M Joyce DPhil

Senior Research Scientist in Molecular Biophysics and Biochemistry; Senior Research Scientist/Scho

Research Interests

DNA polymerase pathway; Dbh polymerase

Research Summary

Structure and mechanism of DNA polymerases
We are using simple DNA polymerases of known structures as model systems to explore the molecular details of DNA replication. In addition to defining the sequence of chemical events involved in the DNA synthesis reaction, we are interested in the molecular processes that ensure polymerase accuracy and the mechanism by which an enzyme can act processively on a macromolecular substrate. Much of our work has focused on DNA polymerase I of E. coli. Based on the wealth of structural information (including a variety of enzyme-substrate complexes) for this polymerase and its homologues, we have used site-directed mutagenesis to make changes in the polymerase active site region. Kinetic studies of the resulting mutant proteins have allowed us to identify protein side chains that recognize the sugar structure of the incoming nucleotide and that influence polymerase accuracy. To learn more about the DNA polymerase reaction pathway, we have started to use fluorescence and EPR techniques to investigate the conformational transitions that take place during the reaction. In recent years, we have expanded our studies to include the Dbh polymerase, a member of the newly discovered family of lesion bypass DNA polymerases. By comparing the highly accurate DNA polymerase I with the extremely inaccurate Dbh, we hope to gain additional insights into those polymerase characteristics that determine fidelity.

Selected Publications

  • DeLucia, A. M., Chaudhuri, S., Potapova, O., Grindley, N.D.F. and Joyce, C. M. The properties of steric gate mutants reveal different constraints within the active sites of Y-family and A-family DNA polymerases. J. Biol. Chem. 281, 27286-27291 (2006)
  • Joyce, C.M. and Benkovic, S.J. DNA polymerase fidelity: kinetics, structure, and checkpoints. Biochemistry 43, 14317-14324 (2004)
  • Purohit, V., Grindley, N.D.F. and Joyce, C.M. Use of 2-aminopurine fluorescence to examine conformational changes during nucleotide incorporation by DNA polymerase I (Klenow fragment). Biochemistry 42, 10200-10211 (2003)
  • Minnick, D.T., Liu, L., Grindley, N.D.F., Kunkel, T.A. and Joyce, C.M. Discrimination against purine-pyrimidine mispairs in the polymerase active site of DNA polymerase I: a structural explanation. Proc. Natl. Acad. Sci. USA 99, 1194-1199 (2002)

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