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Cloning and Functional Characterization of a Sodium-Dependent Phosphate Transporter Expressed in Human Lung and Small Intestine

https://doi.org/10.1006/bbrc.1999.0666Get rights and content

Abstract

A cDNA clone with 53% amino acid identity to the human type II sodium-dependent phosphate transporter (NaPi-3) was isolated from human small intestine and lung. Functional characterization inXenopus laevisoocytes showed this cDNA to encode a sodium-dependent phosphate transporter. The electrogenic response is similar to that found in other type II transporters but an inverse pH dependence was observed. By Northern blot, a 4.2-kb transcript was found to be abundantly expressed in lung and, to a lesser degree, in several other tissues of epithelial origin including small intestine, pancreas, prostate, and kidney. This transcript encompasses a 2.073-kb open reading frame which is most closely related (78% amino acid identity) to the mouse sodium-dependent phosphate transporter IIb isoform. This novel transporter, designated human NaPi-3b (Genbank AF111856), appears to be an isoform of the mammalian renal type II co-transporter family.

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1

To whom correspondence should be addressed at Smithkline Beecham Pharmaceuticals, Dept. of Molecular Biology, UE0548, 709 Swedeland Rd., King of Prussia, PA 19406. Fax: (610) 270-5093. E-mail:[email protected].

2

Current address: Rhone Poulenc Rorer, 500 Arcola Rd., Collegeville, PA 19426.

3

Current address: Laboratory of Molecular and Cellular Neurobiology, National Institues of Health, NIAAA, Bethesda, MD 20892.

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