This is the C-terminal domain (CTD) that can be found in the conserved replication initiator, RepA,essential for staphylococcal propagation. RepA CTD shared the strongest structural homology to the Enterococcus faecalis DnaD CTD, yet perform distinct functions. RepA CTD shows strong sequence homology between RepA_N plasmids in genus-specific clusters, suggesting that it may perform host-specific functions necessary for replication. The RepA CTD interacts with the host DnaG primase, which binds the replicative helicase. Structural data indicate that the RepA CTD exists as a monomeric entity, flexibly tethered to the DNA-bound NTD [1].

1: Mechanism of staphylococcal multiresistance plasmid replication origin assembly by the RepA protein. Schumacher MA, Tonthat NK, Kwong SM, Chinnam NB, Liu MA, Skurray RA, Firth N; Proc Natl Acad Sci U S A. 2014;111:9121-9126. PMID:24927575