Structure of the VcINDY, MtrF, and YdaH transporters. Cartoon representation of the VcINDY (A), MtrF (B), and YdaH (C) dimer structures shown from the extracellular side of the membrane (left). The scaffold domain is colored cyan and dark blue, with the dark blue regions indicating helices involved in oligomerization. The transport domain containing the substrate-binding site(s) is colored green. The helices forming each domain are detailed in the topology diagrams to the right. HPs 1 and 2 correspond to HPin and HPout, respectively, in the nomenclature of Mancusso et al. (2012).