Conjugation: Transfer

Once the acceptor cell has been brought in close, transfer begins. Transfer through the channel is done rolling-circle style: traY gene product nicks the F’ at oriT (a cis element that serves as an origin of replication through rolling circle), and polymerase action pushes the old nicked strand off of the template. This strand is fed through the pilus, and the transfer of the 94.5 kbp F’ factor takes about 5 minutes to complete.


	One important distinction in the F’rolling circle replication cycle is that in order to protect the 5’ end from exonuclease activity, it stays bound to the channel (as shown in the above picture). This prevents the 5’ end from being chopped up until the transfer is complete and the factor can be covalently closed into a circle again.