Figure 4.

Fractional calcium current of N-terminal P2X7aR mutants. A, amino acid sequence of the N terminus of the rP2X7aR was changed one residue at a time to yield 23 mutants. Nineteen of these gave measurable currents in response to 100 μm BzATP. Only E14A and T15A had fractional calcium currents that were significantly different (marked with red lettering the x axis label) from the WT rP2X7aR (wt). The four unresponsive mutants were regenerated in a rP2X7aR-YFP background (I21R*, S23A*, V24R*, and N25A*); of these, only V24A* failed to respond to BzATP. The fractional calcium currents (Pf%) of the other three were significantly smaller than the WT rP2X7aR-YFP (wt*). B, fractional calcium current was measured from a range of rP2X7aR mutants involving Thr¹⁵. Again, results significantly different from the WT rP2X7aR are denoted with red lettering.