Figure 8.

Topological organization of MacB family members. Linear domain arrangement (Left) and transmembrane topologies (Right) are shown for MacB and four representative homologs. From top to bottom, macrolide and toxin transporter MacB, cell division protein FtsEX, lipoprotein trafficking LolCDE, YbbAP (unknown function), bacitracin sensing and efflux protein BceAB. MacB type ABC transporters share a distinctive transmembrane topology although NBDs are not always fused to transmembrane encoding domain and some families exist as apparent fusions of two half-transporters. Sequence identity between the periplasmic domains of each Type VII motif is low, but the extracellular domain of Mycobacterium tuberculosis FtsEX (Mavrici et al., 2014) also contains a Porter subdomain suggesting this could be a common element of Type VII ABC proteins.