Lawrence Berkeley National Laboratory

Maintenance of genomic integrity is extremely important for all organisms. Thus, all cells are equipped with DNA repair mechanisms for different types of DNA damage. The function of the recFOR pathway of recombination is currently not well understood. In E.coli, the recFOR pathway contributes only 0.1-1% of the recombinational activity in the cell (Horii and Clark, 1973) and recF and recR mutants have relatively subtle phenotypes with regard to recombination. Their UV sensitivity is, however, greatly increased. Studies by Courcelle et al. (1997) suggested that recF and recR are required for the resumption of replication at stalled DNA replication forks. Hence, the primary function of proteins in the recFOR pathway in E.coli may not be recombination, but resumption of DNA replication from existing replication forks. In order to get a better understanding of the structure and function of the proteins constituting the RecFOR pathway, we are have purified RecF, RecO, and RecR, and crystallized several of them. The goal is to determine the structure of the proteins alone and/or in complex with each other and with DNA. Currently, diffraction data of RecO crystals with and without bound oligonucleotide have been collected to 2.5 ? and 2.8 ? respectively. Crystals of RecR have been grown but need further improvement. Biochemical experiments provide functional data to determine the partners in complex formation and DNA binding activity of the various complexes. Horii, Z. and Clark, A.J. (1973). J. Mol. Biol. 80, 327-344.Courcelle, J., Carswell-Crumpton, C., Hanawalt, P.C. (1997). Proc. Natl. Acad. Sci. USA 94: 3714-3719.