WHAT DO X-RAY CRYSTALLOGRAPHIC AND ELECTRON-MICROSCOPIC STRUCTURAL STUDIES OF THE RECA PROTEIN TELL US ABOUT RECOMBINATION

The Escherichia coli RecA protein has been the most intensively studied enzyme of homologous recombination. Eukaryotic homologs of RecA are now being found, suggesting that the mechanisms and structures of RecA-mediated recombination may be universal in biology. Most of our knowledge of the structure of the RecA-DNA filament has come from low-resolution electron microscopic studies, but a recent crystallographic study has generated an atomic model for the protein. The interpretation of this model is complicated by the fact that the crystal appears to contain the inactive conformation.