Nucleotide and amino acid sequences of oriT-traM-traJ-traY-traA-traL regions and mobilization of virulence plasmids of Salmonella enterica serovars enteritidis, gallinarum-pullorum, and typhimurium

Abstract

The virulence plasmid of Salmonella enterica serovar Gallinarum-Pullorum (pSPV) but not those of Salmonella enterica serovars Enteritidis (pSEV) and Typhimurium (pSTV) can be readily mobilized by an F or F-like conjugative plasmid. To investigate the reason for the difference, the oriT-traM-traJ-traY-traA-traL regions of the three salmonella virulence plasmids (pSVs) were cloned and their nucleotide and deduced amino acid sequences were examined. The cloned fragments were generally mobilized more readily than the corresponding full-length pSVs, but the recombinant plasmid containing the oriT of pSPV was, as expected, more readily mobilized, with up to 100-fold higher frequency than the recombinant plasmids containing the oriT of the other two pSVs. The nucleotide sequences of the oriT-traM-traJ-traY-traA-traL region of pSEV and pSTV were almost identical (only 4 bp differences), but differed from that of pSPV. Major nucleotide sequence variations were found in traJ, traY, and the Tra protein binding sites sby and sbm. sby of pSPV showed higher similarity than that of pSEV or pSTV to that of the F plasmid. The reverse was true for sbm: similarity was higher with pSEV and pSTV than with pSPV. In the deduced amino acid sequences of the five Tra proteins, major differences were found in TraY: pSEV's TraY was 75 amino acids, pSTV's was 106 amino acids, and pSPV's was 133 amino acids; and there were duplicate consensus betaalphaalpha fragments in the TraY of pSPV and F plasmid, whereas there was only a single betaalphaalpha fragment in that of pSEV and pSTV.

FIG. 1.

Nucleotide sequences of the oriT regions of F plasmid and the three pSVs. Arbitrarily, −157 from the nick site (nic, C-C) of F plasmid is assigned as bp 1, to which all the other sequences are aligned. Colons indicate identical bp. Two boxes with an arrow above indicate the 8-bp inverted repeats. For the other site and gene (locus) designations, see the text and references and . Short arrows facing each other within a pair of short vertical lines indicate the range of the site. Accession numbers: F plasmid sequence, NC_002483; sequences from oriT to traL, AF389529 (pSPV), AF389530 (pSTV), and AF389528 (pSEV).

FIG. 2.

Aligned amino acid sequences of TraY of F plasmid, pSPV, pSEV, and pSTV. Italicized bold letters signify conserved sequences between consensus 1 and 2. Underlined letters denote DNA-binding domains (13). The accession number for R1-19 is M19710. There was only one unit of the βαα segment in pSEV and pSTV, but two are shown here for easy viewing.