We have recently cloned and characterized a functional Na+-dependent vitamin transporter specific for pantothenate and biotin from rat placenta (P.D. Prasad et al., JBC, in press). Since pantothenate and biotin are known to be absorbed in the small intestine via a Na+-dependent transport process, we screened a rabbit intestinal cDNA library using the rat placental pantothenate/biotin transporter cDNA as the probe with an aim to clone the transporter responsible for the intestinal absorption of these vitamins. The screening yielded a positive clone with a 3.3 kbp cDNA insert which, when expressed in HRPE cells, induced Na+-dependent transport of both vitamins. With pantothenate as the substrate, the transport in the presence of NaCl was 7-fold higher in cDNA-transfected cells than in control cells. Substitution of NaCl with choline chloride reduced the transport by 95% in cDNA-transfected cells. With biotin as the substrate, the transport in the presence of NaCl was 12-fold higher in cDNA-transfected cells than in control cells. Replacement of NaCl with choline chloride reduced the transport by 98% in cDNA-transfected cells. Cross inhibition studies showed that lipoate is also a substrate for the cloned transporter. We have also cloned a functional pantothenate/biotin transporter cDNA (3.1 kbp) from Caco-2 cells, a human intestinal cell line.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology