This domain family is found in bacteria, and is typically between 62 and 102 amino acids in length. The family is found in association with Pfam:PF04352. The FinOP (fertility inhibition) system of F-like plasmids consists of an antisense RNA (FinP) and a 22 kDa protein (FinO) which act in concert to prevent the translation of TraJ, the positive regulator of the transfer operon.

1: Differential levels of fertility inhibition among F-like plasmids are related to the cellular concentration of finO mRNA. van Biesen T, Frost LS; Mol Microbiol. 1992;6:771-780. PMID:1374147