The molecular mechanism of conjugative DNA transfer has been studied extensively, especially in Proteobacteria.
The DNA molecule to be transferred (usually a plasmid, that encodes its own transfer apparatus) must carry an origin of transfer (oriT), a short DNA sequence where the
process starts and ends.
The rest of the conjugal machinery consists of no less than 15 proteins that carry out several functions, including the DNA processing reactions and the active transport into the recipient cell.
The conjugalmachinery
can be thought as consisting of three functional modules: