 Many members of this family are predicted to have 11 or 12 transmembrane regions (TMSs); however, one member of this family (Uncharacterized protein of "Encarsia pergandiella" symbiont, "Cardinium hertigii", strain "c"Eper1; TC# 2.A.13.2.1) is reported to have 10 transmembrane regions, with both the N- and C-termini localized to the periplasm.For DcuA, the 'positive inside' rule is obeyed, and two putative TMSs are localized to a cytoplasmic loop between TMSs 5 and 6 and in the C-terminal periplasmic region.The fully sequenced proteins are of fairly uniform size, from 434-446 amino acyl residues in length.