title: A motif conserved among the type I restriction-modification enzymes and antirestriction proteins: a possible basis for mechanism of action of plasmid-encoded antirestriction functions.
abstract: Antirestriction proteins Ard encoded by some self-transmissible plasmids specifically inhibit restriction by members of all three families of type I restriction-modification (R-M) systems in E.coli. Recently, we have identified the amino acid region, 'antirestriction' domain, that is conserved within different plasmid and phage T7-encoded antirestriction proteins and may be involved in interaction with the type I R-M systems. In this paper we demonstrate that this amino acid sequence shares considerable similarity with a well-known conserved sequence (the Argos repeat) found in the DNA sequence specificity (S) polypeptides of type I systems. We suggest that the presence of these similar motifs in restriction and antirestriction proteins may give a structural basis for their interaction and that the antirestriction action of Ard proteins may be a result of the competition between the 'antirestriction' domains of Ard proteins and the similar conserved domains of the S subunits that are believed to play a role in the subunit assembly of type I R-M systems.
authors.affiliation: Department of Genetic Engineering, Cardiology Research Center, Moscow, Russia.
authors.forename: A A
authors.initials: AA
authors.lastname: Belogurov
authors.forename: E P
authors.initials: EP
authors.lastname: Delver
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D004262:DNA Restriction Enzymes / Q000037:antagonists & inhibitors / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology; D008969:Molecular Sequence Data; D010957:Plasmids; D014764:Viral Proteins / Q000737:chemistry*
chemical_list: D014764:Viral Proteins; C019077:anti-restriction proteins; D004262:DNA Restriction Enzymes