Carnitine:γ-butyrobetaine antiporter.  The x-ray structure is known at 3.5 Å resolution (Schulze et al., 2010).  The structure reveals a homotrimer where each protomer has 12 TMSs with 4 L-carnitine molecules outlining the pathway.  There is a central binding site and another in the intracellular vestibule (Tang et al. 2010).

CaiT of E. coli (P31553)

The L-carnitine:γ-butyrobetaine antiporter, CaiT.  The x-ray structure is known at 2.3 Å resolution (Schulze et al., 2010).

CaiT of Proteus mirabilis (B4EY22)