CLONING, SEQUENCE-ANALYSIS AND EXPRESSION OF THE CDNA-ENCODING A SODIUM-DEPENDENT PHOSPHATE TRANSPORTER FROM THE BOVINE RENAL EPITHELIAL-CELL LINE NBL-1

We have isolated a full-length cDNA clone of 2.2 kb from a lambda ZapI I NBL-1 (bovine renal epithelial cell) cDNA library using a portion of the rat renal sodium-dependent phosphate transporter cDNA as a probe. Expression of this cDNA clone in the COS cell line has shown it to sp ecifically encode a sodium-dependent phosphate transporter from bovine renal epithelial cells. Sequence analysis of the clone showed a singl e open reading frame of 693 amino acids which has 70% similarity to th e phosphate transporter of rat and human kidney [Magagnin, S., Werner, A., Markovich, D., Sorribas, V., Stange, G., Biber, J. & Murer, H. (1 993) Proc. Natl Acad. Sci. USA 90, 5979-5983]. Hydropathy plots of the derived amino acid sequence show at least eight possible transmembran e regions, again in agreement with data for the rat and human transpor ters. The sequence contains nine putative N-glycosylation sites and ni ne potential sites for protein kinase C phosphorylation. Previously we have shown that the kinetics of phosphate transport into NBL-1 cells are significantly different to those for opossum kidney cells or rat k idney [Helps, C. & McGivan, J. (1991) Eur J. Biochem. 200, 797-803]. T his difference is presumably related to differences in the amino acid sequence between this protein and other cloned phosphate transporters.