Expression cloning of rat renal Na+/SO4(2-) cotransport.
Injection of rat kidney cortex mRNA into Xenopus laevis oocytes leads to a stimulation of Na(+)-dependent SO4(2-) uptake. Based on this information, we have isolated from a corresponding library a cDNA (NaSi-1) that is most likely related to a Na+/SO4(2-) cotransport system. NaSi-1 cRNA leads in a time- and dose-dependent manner to specific stimulation of Na(+)-dependent SO4(2-) uptake in oocytes. The apparent affinity constants of the NaSi-1 cRNA-expressed transport resemble those of Na+/SO4(2-) cotransport in brush-border membrane. The NaSi-1 cDNA contains 2239 bp [including a poly(A) tail] and encodes a protein of 595 amino acids (66.05 kDa); the hydropathy profile suggests at least eight membrane-spanning regions. In vitro translation of NaSi-1 cRNA results in a protein of the expected size and suggests glycosylation. Northern blot analysis shows signals of 2.3 and 2.9 kb in kidney (more abundant in cortex than in papilla/medulla) and in mucosa of small intestine of rats. The above data indicate that we have structurally identified a membrane protein involved in renal and small-intestinal brush-border membrane Na+/SO4(2-) cotransport.
Markovich
D
D
Institute of Physiology, University of Zürich, Switzerland.
Forgo
J
J
Stange
G
G
Biber
J
J
Murer
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D027682:Cation Transport Proteins; D003001:Cloning, Molecular / Q000379:methods; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D015723:Gene Library; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense; D009865:Oocytes / Q000502:physiology; D009928:Organ Specificity; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates / Q000378:metabolism*; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates; D027981:Symporters; D011061:Poly A; D012313:RNA; D004247:DNA; D012964:Sodium