An origin of transfer (oriT) on the conjugative element pRS01 from Lactococcus lactis subsp. lactis ML3

Abstract

Previous analysis of the Tra1 region of the conjugative element pRS01 from Lactococcus lactis subsp. lactis ML3 suggested that an origin of transfer (oriT) was present. Deletion derivatives of this cloned Tra1 region were assayed for mobilization in the presence of the wild-type pRS01 element in trans. The pRS01 oriT was localized to a 446-nucleotide segment in the intergenic region between open reading frames ltrD and ltrE. Sequence analysis of this region revealed a cluster of direct and inverted repeat structures characteristic of oriT regions associated with other conjugative systems.

FIG. 1

Genetic map of the Tra1 region of pRS01 and results of a pLE12 derivative mobilization analysis. Plasmid pLE12 contains the complete Tra1 region. Plasmids pLE12-1, pLE12-2, and pLE12-4 are deletion derivatives of pLE12. Plasmids pLE12-3, pLE12-5, pLE12-6, and pLE12-7 are deletion derivatives of pLE12-1. The mobilization frequency was calculated by determining the number of transconjugants per input donor.

FIG. 2

Nucleotide sequence of the pRS01 ltrD-ltrE intergenic region. Inverted repeats and direct repeats are indicated by solid arrows and dashed arrows, respectively. Regions homologous to the IncQ (Q1), IncP (P1 through P3), and F (F1) family nic regions are enclosed in boxes.