Complete DNA sequence of the virulence plasmid in Rhodococcus equi

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The complete nucleotide sequence of virulence plasmid pREAT701 from Rhodococcus equi ATCC 33701 has determined. This plasmid contained 80,608pb with 65% GC content. Computer analysis of sequence data revealed that the virulence plasmid encodes 67 open reading frames (ORFs), which occupied 73.5% of the complete sequence. Of the 67 ORFs, 37 ORFs had no significant homology to any known proteins in the current database and the remaining 30 showed significant homologies with previously described hypothetical proteins; 11 are unknown and 19 are functional proteins. We have previously reported that pREAT701 carries a virulence-associated 15- to 17-kDa antigen (VapA) gene. Of the 19 ORFs, 6 ORFs encode proteins that showed significant similarities to VapA, which located between positions 1 to 21,000. GC content is 59%, which is lower than those of the rest of the DNA sequence at positions 21,001 to 80608 (68%) and the chromosomal DNA of R. equi (71%). Insertion elements were scattered throughout the plasmid, indicating the mosaic nature of the virulence plasmid and suggesting evolutionary events by which virulence genes have been obtained.