Alleviation of Type I Restriction in Escherichia coli K12 Carrying the arsR Gene from pKW301 of Acidiphilium multivorum AIU 301

Abstract

Listen

Translate article

INTRODUCTIONConjugal plasmids of various incompatibilitygroups avoid restriction when transferred among var-ious bacterial species and genera. This is mainly dueto the ard ( a lleviation of r estriction of D NA) geneswhich are in the leader region of a plasmid and codefor antirestriction proteins [1–5]. The Ard proteins(ArdA, ArdB, ArdC, ArdU, etc.) are small (140–180amino acid residues), highly acidic (total charge –7 to–30), and nonhomologous to each other, sharing onlyan antirestriction motif [6–9]. The motif is commonlyin the C domain, 30–35 residues away from the C end[10]. Its core consists of nine amino acid residues,with a certain arrangement of negatively charged ones(commonly D/E, highly polar N/Q in one site of ArdBand ArdC) and hydrophobic residues located in thecenter and at the ends (Table 1).We have previously shown that restriction allevia-tion induced by conjugal plasmid R64 (incI1) in Escherichia coli K12 is due to arsR , which codes fora suppressor of the ars operon conferring resistance toarsenite and arsenate [13]. ArsR consists of 117 aminoacid residues, is nonhomologous to the Ard proteins,and contains the antirestriction motif 25–35 residuesaway from the N end [13]. Its antirestriction activity islower than in the Ard proteins: ArsR alleviates restric-tion of nonmodified phage λ DNA by a factor of 20,whereas the factor is about 10