Fig. 4. Mapping of the S100A10 binding site in TRPV5. GST fusion proteins containing different portions of the C-terminal tail of TRPV5 were constructed according to the schematic drawing. These proteins were immobilized on glutathione–Sepharose 4B beads and then incu bated with lysates from X.laevis oocytes injected with 20 ng of S100A10 cRNA. Interaction of S100A10 with the GST fusion proteins was determined by immunoblotting. The binding site was localized between amino acids 598 and 603. Virtually all interaction with S100A10 was abolished when this region (VATTV) was mutated into glycines. A similar effect was observed with the single point mutant TRPV5 T600A.