The λ phage att site: functional limits and interaction with Int protein

Abstract
Site-specific integrative recombination of bacteriophage λ involves unequal partners. The minimal phage att site is composed of approximately 240-base pairs and four distinct binding sites for Int protein, at least three of which are crucial for function. This ‘donor site’ recombines efficiently with a smalle ‘recipient site’ that lacks the extensive interactions with Int protein.