The setB gene is transcribed from a promoter which lies more than 1.5 kb upstream of the setB gene (Behrens et al., 2002). According
to our data, the ardD gene promoter is also located distantly this website from the ardD gene in the region of the mer operon, at a distance of more than 3 kbp. We suggest that other non-conjugative transposons may also contain genes that encode products that can inhibit the restriction endonucleases, thereby efficient overcoming restriction barriers. Note that the tniA gene is usually present in integrons and composite transposons conferring antibiotic resistance and is widely distributed among environmental and clinical bacteria. As an example, the transposon Tn6006 contains a nucleotide sequence identical to ardD in the tniA gene. The Tn6006 transposon MG-132 molecular weight belongs to the group of recombinant transposons containing integrons (Fluit & Schmitz, 1999; Labbate et al., 2008).
This study used equipment of centre of collective use of GosNIIgenetika. It was supported in part by the Russian Foundation for Basic Research (grant 10-04-00541), the Federal Program ‘Scientific and pedagogical innovation resources in Russia, 2009–2013’ (Contract P1070 from 4 June 2010) and The Ministry of Education and Science (Contract 16.522.11.7029). “
“Bacteriocins are the toxic proteins produced by bacteria under stress condition to inhibit the growth of closely related bacterial strain(s). In our earlier study, purified recombinant xenocin–immunity protein complex from Xenorhabdus nematophila showed detrimental effect on six different insect gut residing bacteria. In this study, endogenous toxicity assay with xcinA and its catalytic domain under tightly regulated ara promoter was performed. Multiple sequence alignment and homology modelling revealed six conserved amino acid residues in the catalytic domain of xenocin. Site-directed Resminostat mutagenesis was performed in all the conserved residues, followed growth profile analysis of all the mutants by endogenous toxicity assay. Among the six different conserved sites in catalytic domain of xenocin, we have identified one position where mutation resulted
in no measurable reduction in the endogenous toxicity (K564), three positions with measurable reduction in the endogenous toxicity (E542, H551 and R570) and two positions where mutation caused a significant reduction in the toxicity (D535 and H538). Endogenous toxicity assay is validated by in vitro RNA degradation assay. Structural integrity of purified recombinant proteins was confirmed through circular dichroism and fluorescence spectroscopy. Our results indicate that D535 and H538 act as the acid–base pair for RNA hydrolysis. Bacteriocins are ribosomally encoded, structurally, functionally and ecologically diverse toxins produced by bacteria to inhibit the growth of closely related bacterial strain(s) (Riley & Wertz, 2002; Gordon et al., 2007).