This family includes both TraG and TraD as well as VirD4 proteins. TraG is essential for DNA transfer in bacterial conjugation. These proteins are thought to mediate interactions between the DNA-processing (Dtr) and the mating pair formation (Mpf) systems [1]. This domain interacts with the relaxosome component TraM via the latter's tetramerisation domain. TraD is a hexameric ring ATPase that forms the cytoplasmic face of the conjugative pore [2].

1: TraG-like proteins of DNA transfer systems and of the Helicobacter pylori type IV secretion system: inner membrane gate for exported substrates? Schroder G, Krause S, Zechner EL, Traxler B, Yeo HJ, Lurz R, Waksman G, Lanka E; J Bacteriol 2002;184:2767-2779. PMID:11976307

2: Structural basis of specific TraD-TraM recognition during F plasmid-mediated bacterial conjugation. Lu J, Wong JJ, Edwards RA, Manchak J, Frost LS, Glover JN; Mol Microbiol. 2008;70:89-99. PMID:18717787