This is a bacterial family of cytoplasmic membrane proteins. It includes two transmembrane regions. The molecular function of FxsA is unknown, but in Escherichia coli its over-expression has been shown to alleviate the exclusion of phage T7 in those cells with an F plasmid.

1: Increased synthesis of an Escherichia coli membrane protein suppresses F exclusion of bacteriophage T7. Wang WF, Margolin W, Molineux IJ; J Mol Biol 1999;292:501-512. PMID:10497017