Abstract
An isoform of the mammalian renal type II Na/Pi-cotransporter is described. Homology of this isoform to described mammalian and nonmammalian type II cotransporters is between 57 and 75%. Based on major diversities at the C terminus, the new isoform is designed as type IIb Na/Pi-cotransporter. Na/Pi-cotransport mediated by the type IIb cotransporter was studied in oocytes of Xenopus laevis. The results indicate that type IIb Na/Pi-cotransport is electrogenic and in contrast to the renal type II isoform of opposite pH dependence. Expression of type IIb mRNA was detected in various tissues, including small intestine. The type IIb protein was detected as a 108-kDa protein by Western blots using isolated small intestinal brush border membranes and by immunohistochemistry was localized at the luminal membrane of mouse enterocytes. Expression of the type IIb protein in the brush borders of enterocytes and transport characteristics suggest that the described type IIb Na/Pi-cotransporter represents a candidate for small intestinal apical Na/Pi-cotransport.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Carrier Proteins / chemistry
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Carrier Proteins / genetics
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Carrier Proteins / physiology*
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Cattle
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Female
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Flounder
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Genetic Variation
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Intestinal Mucosa / metabolism*
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Intestine, Small / metabolism*
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Kidney / metabolism
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Mammals
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Mice
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Molecular Sequence Data
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Oocytes / physiology
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Organ Specificity
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Phosphates / metabolism
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Phosphates / pharmacology
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Protein Isoforms / chemistry
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Protein Isoforms / genetics
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Protein Isoforms / physiology
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RNA, Messenger
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Sequence Alignment
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Sequence Homology, Amino Acid
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Sodium / metabolism
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Sodium / pharmacology
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Sodium-Phosphate Cotransporter Proteins
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Sodium-Phosphate Cotransporter Proteins, Type II
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Sodium-Phosphate Cotransporter Proteins, Type IIb
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Symporters*
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Transcription, Genetic
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Xenopus laevis
Substances
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Carrier Proteins
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Phosphates
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Protein Isoforms
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RNA, Messenger
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Slc34a2 protein, mouse
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Sodium-Phosphate Cotransporter Proteins
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Sodium-Phosphate Cotransporter Proteins, Type II
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Sodium-Phosphate Cotransporter Proteins, Type IIb
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Symporters
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Sodium