Open AccessThe Lla GI restriction and modification system of Lactococcus lactis W10 consists of only one single polypeptide
Author(s) -
Madsen Annette,
Josephsen Jytte
Publication year - 2001
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2001.tb10698.x
Subject(s) - lactococcus lactis , plasmid , operon , biology , restriction enzyme , genetics , gene , dna , bacteriophage , restriction map , microbiology and biotechnology , bacteria , escherichia coli , lactic acid
The naturally occurring 12.1‐kb plasmid, pEW104, in Lactococcus lactis ssp. cremoris W10 was found to confer decreased bacteriophage sensitivity to its host. Plasmid pEW104 encodes a non‐classic restriction and modification (R/M) system, named Lla GI, consisting of only one single polypeptide. Analysis of the amino acid sequence revealed the presence of a catalytic motif and seven helicase‐like motifs (DEAD‐box motifs) characteristic of type I and III endonucleases, followed by four conserved methylase motifs characteristic of adenine‐methylases. A comparison between Lla GI and the very similar R/M system, Lla BIII, suggests that the C‐terminal region of Lla GI, apparently containing no known motifs, could possibly specify target DNA recognition. Conceivably, the Lla GI gene is included in the operon of the plasmid replication machinery. Finally, it is proposed that Lla GI represents a variant of the type I R/M systems.