Direct role of the himA gene product in phage lambda integration

The integration of phage lambda into the Escherichia coli chromosome is accomplished by a site-specific recombination between two unique DNA sequences (attB on the bacterial genome and attP on the phage; reviewed in refs 2, 3) and requires proteins encoded by both the bacterium and the phage. Genetic and biochemical studies have shown that bacterial strains mutant in the himA gene, located at 38 min on the E. coli map, are defective in the activity of the host-encoded component. They are, moreover, defective for the growth of bacteriophage Mu, for precise excision of transposable antibiotic resistance determinants and for the synthesis of the lambda int gene product. We now show that the himA gene product (phimA) is not solely a regulator of genes involved in integration but is one of two host polypeptides required for integrative recombination.