PLASMID-DERIVED TYPE II RESTRICTION-MODIFICATION SYSTEMS FROM LACTOCOCCUS LACTIS

摘要

A number of type II restriction-modification (R-M) systems have been derivedfrom plasmids found in Lactococcus lactis strains from the Danish starterculture TK5. The R-M systems LlaAI, LlaBI and LlaDII are claimed with theirnucleotide sequences containing open reading frames (ORFs) coding forrestriction endonucleases and corresponding methylases. Also a DNA cassettecomprising one or more of the R-M systems and fragments thereof in combinationwith DNA encoding other phage resistance mechanisms is claimed as are cloningand expression vectors including DNA selected from the group consisting of theR-M systems, fragments thereof and DNA cassette, cells transformed with theexpression vectors, a method of conferring increased virus resistance on acell, and the individual restriction endonucleases and methylases of the R-Msystems.