Other TH secondary transporters include the aromatic amino acid transporter MCT10, the organic anion transporting polypeptide transporters (e.g., OATP1C1
, OATP1A2, and OPTP1A4), the large neutral amino acid transporters (LAT1 and LAT2), and another amino acid transporter, the L-cystine and L-glutamate exchanger.
In contrast, when the equivalent tryptophans were mutated individually and as a double mutant to phenylalanine in rat OATP1C1, protein function was preserved [21,22].
However the double tryptophans in rat OATP1C1 retained wild type characteristics when mutated to phenylalanine , suggesting that different OATPs may be able to function with the phenylalanine substitution.
Rumbley, "Evidence of evolutionary conservation of function between the thyroxine transporter Oatp1c1 and major facilitator superfamily members," Endocrinology, vol.
The fourth member, OATP1C1, is regarded as thyroid hormone transporter, because of its high affinity for the thyroid hormones [T.sub.3] and [T.sub.4] .
OATP1C1. OATP1C1 is a transporter with the highest affinity for thyroid hormones, and it could be important for the transport of these hormones in target tissues.