Alleviation of type I restriction in Escherichia coli K12 carrying the arsR gene from pKW301 of Acidiphilium multivorum AIU 301

A study was made of the antirestriction activity of Acidiphilium multivorum AIU 301 ArsR, a repressor of the acr operon which confers resistance to ar senite and arsenate and is contained in pKW301. In Escherichia coli, arsR c loned under the control of P-lac in a multicopy vector alleviated restricti on of nonmodified lambda DNA by a factor of 120, six times more efficiently than its analogs of conjugal plasmids R64 (incI1) and R773 (incFI). Amino acid sequence analysis showed that the three ArsR proteins have a homologou s region of 38 residues, including the antirestriction motif, in their N do mains, whereas in the Ard proteins the motif is in the C domain. The other regions are nonhomologous, and pKW301 ArsR is 33 residues shorter than R64 and R773 ArsRs. The total charge is -4 in pKW301 ArsR and +2 in R64 and R73 3 ArsRs. A total negative charge was assumed to contribute to the antirestr iction activity.