A family of phase-variable restriction enzymes with differing specificities generated by high-frequency gene rearrangements.

ABSTRACT: The hsd genes of Mycoplasma pulmonis encode restriction and modification enzymes exhibiting a high degree of sequence similarity to the type I enzymes of enteric bacteria. The S subunits of type I systems dictate the DNA sequence specificity of the holoenzyme and are required for both the restriction and the modification reactions. The M. pulmonis chromosome has two hsd loci, both of which contain two hsdS genes each and are complex, site-specific DNA inversion systems. Embedded within the coding region of each hsdS gene are a minimum of three sites at which DNA inversions occur to generate extensive amino acid sequence variations in the predicted S subunits. We show that the polymorphic hsdS genes produced by gene rearrangement encode a family of functional S subunits with differing DNA s

SUBMITTER: Dybvig K 

PROVIDER: S-EPMC24968 | biostudies-literature | 1998 Nov

REPOSITORIES: biostudies-literature