Functions as a transporter for creatine and as well for its precursor guanidinoacetate. Transport of creatine and GAA is independent of resting membrane potential and extracellular Na(+), Cl(-), or pH. Contributes to the process of creatine biosynthesis and distribution.
Subcellular locations: Cell membrane, Basolateral cell membrane
Interaction with isoform 2 of BSG is required for its localization to the plasma membrane.
Most highly expressed in kidney, followed by retina, lung, heart and testis. Very weakly expressed in brain and liver. Also detected in lens.