Riboflavin Transporter 2 (RFT2)

Biochemical characterization revealed that riboflavin uptake by rat Rft2 was saturable and Na(+) independent, with a pH optimum between 5 and 6. Riboflavin appeared to be the primary molecule transported by Rft2. Riboflavin transport could be competitively inhibited by the riboflavin derivatives lumiflavin, flavin mononucleotide, and flavin adenine dinucleotide, and to a lesser extent by alloxazine and the organic cation amiloride, but not by D-ribose or organic anions. The deduced 469-amino acid protein shares 83% similarity with rat Rft2, which contains 11 potential membrane-spanning domains and a putative N-glycosylation site. Northern blot analysis of rat tissues showed highest Rft2 expression in jejunum, ileum, and testis, with lower expression in lung, kidney, stomach, and colon.