Note that other ORFs found along the complementary strand in the region of the genes tni Tn5053 do not contain RBS sequence upstream of the initiation codon. To test the hypothesis of antirestriction activity of orf-5, we constructed a hybrid plasmid using the 2300-bp KpnI-SalI DNA fragment from orf-5 containing region tniA,B,Q. This fragment

was cloned under the lac promoter in vector pUC18 (pTLORF-5, Fig. 1). Introduction of this plasmid into cells of strain NK114 produced an antirestriction effect similar to that observed for the wild-type Tn5053, about 100-fold (Table 2). Internal deletion in the orf-5 gene was produced by Eco47III restriction endonuclease treatment of pTLORF-5. In the resulting plasmid pSMΔORF-5, a major part of orf-5 (245 bp; nucleotides 7621–7866 in the L40585 PLX4032 supplier sequence) was deleted, including the putative antirestriction motif VVDVVDDKA (Fig. 2). Z-VAD-FMK molecular weight The antirestriction effect in E. coli NK114 cells, containing pSMΔORF-5, disappeared completely (Table 2). For further evaluation of the role of orf-5 in this antirestriction effect, we amplified orf-5 together with the RBS and cloned them in pUC19 under the lac promoter (for details see Materials and methods). After the plasmid obtained (pORF-5) was introduced into NK114 cells, the antirectriction factor R was estimated. Plasmid pORF-5 showed a considerable antirestriction effect: efficiency

of the λ.0 phage plating was about 500-fold higher than the control level (cells with pUC19) (Table 2). It has been shown that the genes encoding the antirestriction proteins

(ArdA, ArdB, ArdC) may be located within conjugative plasmids and conjugative transposons (Delver et al., 1991; Belogurov et al., 1993, 2000; McMaahon et al., 2009; Serfiotis-Mitsa et al., 2010). Here we show for the first time that a similar gene is also present within a non-conjugative transposon (Tn5053). Analysis of the deduced amino acid sequence of ORF-5 revealed that this protein has no similarities to the known Ard proteins (ArdA, ArdB and ArdC types) except the ‘antirestriction’ motif conserved for all known Ard proteins. This suggests that ORF-5 may be classified as a new type of Ard protein, which we designate ArdD. The N-terminal region of ArdD has a high degree of similarity (about 39% identity and 53% similarity) Paclitaxel manufacturer to the region of the MerR protein (312–367 amino acids) of Desulfovibrio vulgaris strain ‘Miyazaki F’ (NCBI reference sequence YP_002436545.1; Fig. 3). Interestingly, the total negative charge of homologous sequences ArdD and MerR is virtually the same, −5 and −7, respectively. The location of the ardD gene appears to be unusual: inside a transposition gene (tniA) with transcription at the complementary strand (Fig. 1). Overlapping genes in bacterial genomes are rare. For example, most strains of Shigella flexneri 2a and enteroaggregative E.