The extent of DNA sequence required for a functional bacterial attachment site of phage lambda.

We have investigated the extent of DNA sequence required to form a bacterial attachment site (attB) that functions in bacteriophage lambda integration. A DNA fragment carrying attB of Escherichia coli was trimmed, recloned and tested for recombination proficiency. We found that the common core sequence plus the adjoining 4-bp sequences of both the B and B' arms are required for full activity, while plasmids with an even shorter attB sequence retain some capacity to function as attB in vivo. We also found that the nonspecific DNA that is joined to the required attachment site sequence does not significantly influence the rate of the recombination reaction.