Purification and some of the functions of the products of bacteriophage T4 recombination genes, uvsX and uvsY.

The nonessential T4 genes uvsX and uvsY are involved in DNA repair and general recombination. Using newly isolated amber mutants of these genes, we have identified the gene products (gp) by sodium dodecyl sulfate (SDS)/polyacrylamide gel electrophoresis. Their relative molecular masses are 39 000 and 16 000, respectively. In the normal wild-type infection process they are produced early but not late in infection. Their synthesis continues for a longer period when DNA synthesis is blocked. We have developed procedures to isolate these gene products at a purity of more than 95% for gpuvsX and at 70% for gpuvsY, as judged by SDS/polyacrylamide gel electrophoresis and staining with Coomassie brilliant blue dye. The purification procedures suggest that these products may be membrane proteins. Using both an agarose gel assay and electron microscopy, we find that the product of the gene uvsX catalyzes the assimilation of a linear single-stranded fd DNA fragment into superhelical double-stranded fd DNA (RFI). The reaction requires ATP and Mg2+ besides substrate DNAs and uvsX protein. The T4 uvsX protein therefore is similar to the Escherichia coli recA protein in molecular size and function, but differs in antigenic property.