Figure 8.

Effects of MTSES on IKCa mutants. Inside-out current records measured in symmetrical 200 mM K₂SO₄ + 3 μM internal Ca²⁺ conditions. The pipette potential was 60 mV throughout. In contrast to MTSET, MTSES failed to cause over a 5 min period a significant decrease of the V275C-induced currents. As observed with MTSET, however, MTSES succeeded in strongly inhibiting the V284C mutant and to stimulate the inward currents generated by A283C and A286C. Also illustrated are MTSES protection experiments performed on V275C and A286C, where MTSES (5 mM) was applied prior MTSET (5 mM). These experiments confirmed that a cysteine at position 275 is not accessible to MTSES and that the binding of MTSET to 286C prevents the interaction of MTSES–A286C.