This family consists of several bacterial TrfA proteins. The trfA operon of broad-host-range IncP plasmids is essential to activate the origin of vegetative replication in diverse species. The trfA operon encodes two ORFs. The first ORF is highly conserved and encodes a putative single-stranded DNA binding protein (Ssb). The second, trfA, contains two translational starts as in the IncP alpha plasmids, generating related polypeptides of 406 (TrfA1) and 282 (TrfA2) amino acids. TrfA2 is very similar to the IncP alpha product, whereas the N-terminal region of TrfA1 shows very little similarity to the equivalent region of IncP alpha TrfA1. This region has been implicated in the ability of IncP alpha plasmids to replicate efficiently in Pseudomonas aeruginosa [1].

1: Conservation of the genetic switch between replication and transfer genes of IncP plasmids but divergence of the replication functions which are major host-range determinants. Thorsted PB, Shah DS, Macartney D, Kostelidou K, Thomas CM; Plasmid 1996;36:95-111. PMID:8954881