The 2 identical subunits are oriented in opposite directions. The helices are anti-parallel with respect to their 2 near neighbors. The longer tail is the N-terminus.

ROP is a protein encoded by plasmids that reduces the copy number of the plasmid by interfering with DNA replication.

Banner, D. W., Kokkinidis, M., Tsernoglou, D.: Structure of the ColE1 rop protein at 1.7 A resolution. J Mol Biol 196 pp. 657 (1987)
(PubMed)

1rop (PDB)