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. Author manuscript; available in PMC: 2015 Aug 1.
Published in final edited form as: Curr Opin Struct Biol. 2014 Mar 28;0:8–15. doi: 10.1016/j.sbi.2014.02.007

Figure 3. The transport of bile acids by ASBT and dicarboxylates by an INDY homologue dicarboxylate transporter.

Figure 3

A. Bile acids such as taurocholic acid (spheres) are transported by the ASBT transporter (top, light blue/magenta/dark blue). The structure led to the suggested mechanism where taurocholic acid binds ASBT in the outward facing conformation, undergoes a horizontal positioning along a putative dual-access binding site, and is then imported and released following a conformational change to the inward facing conformation. The pathway for import is indicated by dashed arrows. This has been proposed to be dependent on Na+ binding and requires slight changes in both TM4 and TM9. B. VcINDY (top, blue/gold) is a dicarboxylate transporter that was solved in the presence of citrate (red/gray spheres) and Na+ (green spheres). The import pathway is indicated by dashed arrows, with a periplasmic view of the structure shown in the middle panel. The bottom panel is a zoomed view of the citrate binding pocket along with the observed Na+ site (left, green sphere) and the putative Na+ binding site (right, green sphere), both of which are important for transport.