Members of this family are integral membrane proteins. Some are involved in drug resistance. AcrB cooperates with a membrane fusion protein, AcrA, and an outer membrane channel TolC. The structure shows the AcrB forms a homotrimer [1].

1: Crystal structure of bacterial multidrug efflux transporter AcrB. Murakami S, Nakashima R, Yamashita E, Yamaguchi A; Nature 2002;419:587-593. PMID:12374972