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