cDNA cloning of a rat small-intestinal Na+/SO4(2-) cotransporter.
We have isolated a cDNA (ileal NaSi-1) from rat small intestine by homology screening with a cDNA (renal NaSi-1) encoding rat kidney cortex Na(+)-SO4(2-) cotransport. Ileal NaSi-1 cRNA specifically stimulates Na(+)-dependent SO4(2-) uptake in a time- and dose-dependent manner in Xenopus laevis oocytes, with kinetic parameters almost identical to those of the renal NaSi-1. Ileal NaSi-1 cDNA contains 2722 base pairs (bp), almost 500 bp more than the renal NaSi-1 cDNA; however, it encodes a protein of 595 amino acids identical to the renal NaSi-1 protein. Northern blot analysis shows strong signals in rat lower small intestine and kidney cortex (2.9 x 10(3) and 2.3 x 10(3) bases), with the ileal NaSi-1 corresponding to the longer transcript. We conclude that we have identified a rat ileal cDNA that encodes a membrane protein most likely involved in brush-border Na(+)-SO4(2-) cotransport. It differs to the renal NaSi-1 only in the length of the 3' untranslated region, suggesting that the major difference lies in the differential use of polyadenylation signals.
Norbis
F
F
University of Zürich, Institute of Physiology, Switzerland.
Perego
C
C
Markovich
D
D
Stange
G
G
Verri
T
T
Murer
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D027682:Cation Transport Proteins; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D005260:Female; D007421:Intestine, Small / Q000378:metabolism*; D008969:Molecular Sequence Data; D009865:Oocytes; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D000077003:Sodium Sulfate Cotransporter; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D000077003:Sodium Sulfate Cotransporter; D027981:Symporters