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2.A.125 The Eukaryotic Riboflavin Transporter (E-RFT) Family

Human and rat plasma membrane riboflavin transporters, hRFT1 and rRFT1, were identified on the basis of a rat kidney mRNA expression database (Horiba et al. 2004). hRFT1 and rRFT1 cDNAs have an open reading frame encoding 448- and 450-amino acid proteins, respectively. Overexpression of hRFT1 or rRFT1 increased the cellular accumulation of [(3)H]riboflavin (Yonezawa et al. 2008). The transfection of small interfering RNA targeting both hRFT1 and hRFT1sv significantly decreased the uptake of [(3)H]riboflavin by HEK-293 and Caco-2 cells. Riboflavin (Km ≈ 40μM) transport is Na+, potential, and pH independent. RFT1 shows low similarity with the TRAP-T porters (2.A.56), nucleoside transporters (2.A.57) and aromatic acid porters (2.A.1.15).

The generalized reaction catalyzed by RFT1 is:

riboflavin (out) ⇌ riboflavin (in)

References associated with 2.A.125 family:

Horiba, N., S. Masuda, A. Takeuchi, H. Saito, M. Okuda, and K. Inui. (2004). Gene expression variance based on random sequencing in rat remnant kidney. Kidney Int 66: 29-45. 15200410
Yonezawa, A., S. Masuda, T. Katsura, and K. Inui. (2008). Identification and functional characterization of a novel human and rat riboflavin transporter, RFT1. Am. J. Physiol. Cell Physiol. 295: C632-641. 18632736