The BCCT family proteins vary in length between 481 and 706 amino acyl residues and possess 12 putative transmembrane α-helical spanners (TMSs).

Both CaiT structures (SWSW​, 4M8J​) show the fully open, inward-facing conformation and thus complete the set of functional states that describe the alternating access mechanism.

Crystal structures of CaiT from E. coli and Proteus mirabilis revealed the inverted five-transmembrane-helix repeat similar to that in the amino acid/Na+ symporter, LeuT.

Kalayil et al. (2013) showed that mutations of arginine 262 (R262) made CaiT Na+-dependent with increased transport activity in the presence of membrane potential, in agreement with substrate/Na+ cotransport.

The oscillation of the R262 side chain in CaiT indicates how a positive charge triggers the change between outward-open and inward-open conformations.