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Báo cáo khoa học: Evolutionary and experimental analyses of inorganic phosphate transporter PiT family reveals two related signature sequences harboring highly conserved aspartic acids critical for sodium-dependent phosphate transport function of human PiT2

The mammalian members of the inorganic phosphate (Pi ) transporter (PiT) family, the type III sodium-dependent phosphate (NaP i) transporters PiT1 and PiT2, have been assigned housekeeping Pi transport functions and are suggested to be involved in chondroblastic and osteoblastic mineralization and ectopic calcification. | iFEBS Journal Evolutionary and experimental analyses of inorganic phosphate transporter PiT family reveals two related signature sequences harboring highly conserved aspartic acids critical for sodium-dependent phosphate transport function of human PiT2 Pernille B0ttger1 2 and Lene Pedersen1 2 1 Department of Molecular Biology Aarhus University Denmark 2 Institute of ClinicalMedicine Aarhus University Denmark Keywords PiT2 retroviralreceptor sequence logo signature sequence type III sodiumdependent phosphate symporter Correspondence L. Pedersen Department of Molecular Biology Aarhus University C. F. Mollers Alle Bldg. 130 DK-8000 Aarhus C Denmark Fax 45 86196500 Tel 45 89422633 E-mail LP@mb.au.dk http www.mb.au.dk and http www.ki.au.dk Received 22 February 2005 revised 8 April 2005 accepted 18 April 2005 doi 10.1111 j.1742-4658.2005.04720.x The mammalian members of the inorganic phosphate Pi transporter PiT family the type III sodium-dependent phosphate NaPi transporters PiT1 and PiT2 have been assigned housekeeping Pi transport functions and are suggested to be involved in chondroblastic and osteoblastic mineralization and ectopic calcification. The PiT family members are conserved throughout all kingdoms and use either sodium Na or proton H gradients to transport Pi. Sequence logo analyses revealed that independent of their cation dependency these proteins harbor conserved signature sequences in their N- and C-terminal ends with the common core consensus sequence GANDVANA. With the exception of 10 proteins from extremophiles all 109 proteins analyzed carry an aspartic acid in one or both of the signature sequences. We changed either of the highly conserved aspartates Asp28 and Asp506 in the N- and C-terminal signature sequences respectively of human PiT2 to asparagine and analyzed Pi uptake function in Xenopus laevis oocytes. Both mutant proteins were expressed at the cell surface of the oocytes but exhibited knocked out NaPi transport function. Human PiT2 is .