Dimerization of the bacterial RsrI N6-adenine DNA methyltransferase.

ABSTRACT: Dimeric restriction endonucleases and monomeric modification methyltransferases were long accepted as the structural paradigm for Type II restriction systems. Recent studies, however, have revealed an increasing number of apparently dimeric DNA methyltransferases. Our initial characterization of RsrI methyltransferase (M.RsrI) was consistent with the enzyme functioning as a monomer, but, subsequently, the enzyme crystallized as a dimer with 1500 A2 of buried surface area. This result led us to re-examine the biochemical properties of M.RsrI. Gel-shift studies of M.RsrI binding to DNA suggested that binding cooperativity targets hemimethylated DNA preferentially over unmethylated DNA. Size-exclusion chromatography indicated that the M.RsrI-DNA complex had a size and stoichiometry consistent

SUBMITTER: Thomas CB 

PROVIDER: S-EPMC1361615 | biostudies-literature | 2006

REPOSITORIES: biostudies-literature