Intestinal folate transport: identification of a cDNA involved in folate transport and the functional expression and distribution of its mRNA.

摘要: Abstract Although the mechanism of folate intestinal transport has been subject intensive studies, very little is known about molecular iventity system(s) involved. In this investigation, we screened a mouse cDNA library using as probe clone reduced carrier ( RFC1 ) leukemia L1210 cells, and identified positive clone, IFC1(RFC1) . The cloned consisted 2274 base pairs with an open reading frame that encoves putative polypeptive 512 amino acids predicted mass 58 112 daltons 12 transmembrane domains. appears to carry net charge (p I = 8.6) which may be important for its interaction negatively charged substrate. Functional was established by expression in Xenopus oocytes. An 11-fold increase 5-methyltetrahydrofolate (5-MTHF) uptake observed oocytes injected 10 ng cRNA compared water-injected controls. expressed oocyte was: (1) 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS)-sensitive; (2) saturable apparent K m 1.99 ± 0.32 μ M, V max 3782 188 fmol/oocyte per h. distribution mRNA species complementary different tissues examined Northern blot analysis. addition small intestine, such were also found kidney, large brain, heart liver. Furthermore, vetected analysis intestine human other animal (rat rabbit). Expression markedly higher rat villus cells than crypt cells. These results represent first iventification transporter mammalian intestine.