MX35 epitope mapping. (A) Schematic diagram of the predicted membrane topology of the sodium-dependent phosphate transporter 2b protein. (B) Schematic presentation of the NaPi2b protein and fusion proteins derived from the potentially largest extracellular region (aa 188-361) and the location of the MX35 epitope. (C) NaPi2b fusion proteins expressed in bacteria and immunoblotted with mAb MX35 after separation by SDS-PAGE.