Molecular and functional characterization of the intestinal Na+-dependent multivitamin transporter.
We have cloned a Na+-dependent multivitamin transporter from rabbit intestine (riSMVT). The cDNA codes for a protein of 636 amino acids with 12 putative transmembrane domains. When expressed in mammalian cells, the cDNA induces Na+-dependent uptake of the vitamins pantothenate and biotin. Lipoate is also a substrate for the cDNA-induced uptake process. The affinity constant for the cDNA-specific transport of pantothenate and biotin is approximately 2 and approximately 8 microM, respectively. The Na+:vitamin stoichiometry is greater than 1, indicating that the transport process is electrogenic. The SMVT-specific transcripts of 3.2 kbp are equally distributed throughout the small intestine. We have also cloned SMVT from the human intestinal cell line Caco-2. The Caco-2 SMVT cDNA codes for a protein of 635 amino acids which is homologous to riSMVT and is identical to the SMVT expressed in the human choriocarcinoma cell line JAR. Caco-2 SMVT also catalyzes Na+-dependent uptake of pantothenate, biotin, and lipoate. In oocytes expressing Caco-2 SMVT, all three vitamins evoke inward currents, confirming the electrogenicity of the transport process.
Prasad
P D
PD
Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, Georgia, 30912, USA. pprasad@mail.mcg.edu
Wang
H
H
Huang
W
W
Fei
Y J
YJ
Leibach
F H
FH
Devoe
L D
LD
Ganapathy
V
V
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001710:Biotin / Q000378:metabolism*; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010205:Pantothenic Acid / Q000378:metabolism*; D011487:Protein Conformation; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D027981:Symporters; C119981:biotin transporter; D010205:Pantothenic Acid; D001710:Biotin