fertility inhibition factors, including OSA and FiwA, related to the ParB/Srx superfamily
Osa and FiwA are fertility inhibition factors (FIN), which are employed by plasmids to block import of rival plasmids. Osa (oncogenic suppressive activity) of IncW group plasmid pSa gene inhibits the oncogenic properties of Agrobacterium tumefaciens. Osa is structurally similar to the ParB N-terminal domain/Srx superfamily of proteins: ParB acts in the bacterial and plasmid parABS partitioning systems. Osa has been shown to have ATPase and DNAse activities, an can block T-DNA transfer into plants. FiwA is encoded by plasmid RP1 and blocks the transfer of plasmid R388. The gene product of Haemophilus influenzae p1056.10c also blocks T-DNA transfer.