Expression cloning and cDNA sequencing of the Na+/glucose co-transporter.
Organic substrates (sugars, amino acids, carboxylic acids and neutrotransmitters) are actively transported into eukaryotic cells by Na+ co-transport. Some of the transport proteins have been identified--for example, intestinal brush border Na+/glucose and Na+/proline transporters and the brain Na+/CI-/GABA transporter--and progress has been made in locating their active sites and probing their conformational states. The archetypical Na+-driven transporter is the intestinal brush border Na+/glucose co-transporter (see ref. 8), and a defect in the co-transporter is the origin of the congenital glucose-galactose malabsorption syndrome. Here we describe cloning of this co-transporter by a method new to membrane proteins. We have sequenced the cloned DNA and have found no homology between the Na+/glucose co-transporter and either the mammalian facilitated glucose carrier or the bacterial sugar transport proteins. This suggests that the mammalian Na+-driven transporter has no evolutionary relationship to the other sugar transporters.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D005260:Female; D006352:Heart Ventricles / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics*; D009865:Oocytes / Q000378:metabolism; D011061:Poly A / Q000235:genetics; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D014158:Transcription, Genetic; D014982:Xenopus laevis
D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D004247:DNA