An E. coli gene product required for lambda site-specific recombination.

We report characteristics of himA mutations of E. coli, selected for their inability to support the site-specific recombination reaction involved in the formation of lysogens by bacteriophage lambda. The himA allele lies at minute 38 on the chromosome. Three noncomplementing and closely linked mutations define the himA locus; one is a nonsense mutation which shows that the gene product is a protein. HimA mutations reduce both lambda integrative and excisive site-specific recombination. Since dominance tests demonstrate that himA mutations are recessive, it is probable that the himA protein is either a necessary component for site-specific recombination or, alternatively, regulates the expression of such a function. HimA mutations exhibit pleiotropic effects. They reduce integration of phages that have different attachment specificities from lambda and inhibit the growth of phage mu. In addition, himA mutations reduce precise excision of integrated phage mu as well as Tn elements. This pleiotropy suggests that the role of himA protein is nonspecific. Since all of the processes affected by himA mutations ultimately rely on protein-DNA interactions, we suggest that himA protein may act in an auxillary manner to facilitate these interactions.