Fig. 1.

Conjugative plasmids employ proteins encoded on the leading region to antagonize defense systems in the recipient cell. The backbone of a generic CP is composed of the tra region that encodes all proteins necessary in conjugal transfer (green); the origin of transfer oriT (red); the leading region (blue), which is the first part of the CP transferred to the recipient cell coupled to the relaxase (purple) in a ssDNA form. Frpo-type promoters present on the leading region, when in ssDNA form, transiently switches on expression of genes encoding proteins (blue box) necessary to thwart host defense systems against foreign DNA (red box) in the recipient cell. Cas CRISPR-associated, CP conjugative plasmid, CRISPR clustered regularly interspaced short palindromic repeats, SSB single-stranded DNA binding, T4CP type IV coupling protein