Cloning and functional characterization of the human sodium-dependent vitamin C transporters hSVCT1 and hSVCT2.
Two sodium-dependent vitamin C transporters, hSVCT1 and hSVCT2, were cloned from a human kidney cDNA library. hSVCT1 had a 1797 bp open reading frame encoding a 598 amino acid polypeptide. The 1953 bp open reading frame of hSVCT2 encoded a 650 amino acid polypeptide. Using a Xenopus laevis oocyte expression system, both transporters were functionally expressed. By Eadie-Hofstee transformation the apparent K(m) of hSVCT1 for ascorbate was 252.0 microM and of hSVCT2 for ascorbate was 21.3 microM. Both transporters were sodium-dependent and did not transport dehydroascorbic acid. Incubation of oocytes expressing either transporter with phorbol 12-myristate 13-acetate (PMA) inhibited ascorbate transport activity. Availability of the human transporter clones may facilitate new strategies for determining vitamin C intake.
Daruwala
R
R
Molecular and Clinical Nutrition Section, Bldg. 10, Rm. 4D52, MSC 1372, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1372, USA.
Song
J
J
Koh
W S
WS
Rumsey
S C
SC
Levine
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D003001:Cloning, Molecular; D005260:Female; D006801:Humans; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D029363:Organic Anion Transporters, Sodium-Dependent; D014176:Protein Biosynthesis; D011506:Proteins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D012964:Sodium / Q000502:physiology*; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014982:Xenopus laevis
D002352:Carrier Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D011506:Proteins; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D003994:Bucladesine; D012964:Sodium; D013755:Tetradecanoylphorbol Acetate; D001205:Ascorbic Acid