A novel gene, ardD, determines antirestriction activity of the non-conjugative transposon Tn5053 and is located antisense within the tniA gene

Abstract

The mercury-resistance transposon Tn5053 inhibits restriction activity of the type I restriction-modification endonuclease EcoKI in Escherichia coli K12 cells. This is the first report of antirestriction activity of a non-conjugative transposon. The gene (ardD) coding for the antirestriction protein has been cloned. The ardD gene is located within the tniA gene, coding for transposase, on the complementary strand. The direction of transcription is opposite to transcription of the tniA gene.

Fig 1

Structure of pKLH53.1, subcloned fragments, insertion and deletion mutants. EV, EcoRV; Bc, BclI; Bs, BssHII; Cl, ClaI; D, DraI; E, EcoRI; Ac, Acc65I; H, HindIII; Hp, HpaI; K, KpnI; N, NdeI; P, PvuII; S, SalI.

Fig 2

Nucleotide sequence of the gene orf-5 (ardD) and amino acid sequence of its product (147 amino acids), encoded by the complementary strand of the gene tniA in transposon Tn5053. RBS is shown in italics and underlined, a putative antirestriction motif is shown in italics and Eco47III sites are underlined.

Fig 3

Comparison of the amino acid sequences of ArdD (Tn5053) and MerR (Desulfovibrio vulgaris strain ‘Miyazaki F’). Aligment was done with the program NCBI blast. ArdD (2–58 amino acids) and MerR (312–367 amino acids) homologous regions: identity = 39%, similarity = 53%.