MscS and MscL adapt when expressed in E. coli spheroplasts separately or together. (A and B) A comparison of dose–response curves taken with a series of pressure steps and a 1-s linear ramp from 0 to saturating pressure. Pairs of dose–response curves are shown for MscS (A) and MscL (B) individually expressed in MJF465 spheroplasts. Insets show current responses of the excised patch to the series of pressure steps, with a machine-limited 10-ms raise time. The ramp-generated curves are always right-shifted by 10–20% on the pressure scale. For MscS (A), maximal current was 1.4 nA and ramp p_0.5 = 95 mmHg. For MscL (B), saturating current was 3.14 nA and p_0.5 = 255 mmHg with the ramp stimulus. (C–E) MscS and MscL show similar tension- and time-dependent decline of currents when coexpressed in PB113 spheroplasts carrying a native copy of the mscL gene. Both channels were probed with 3-s pressure steps of varying amplitude. MscS activates in the lower range of pressures (C), whereas MscL (D) had to be probed with pressures twice as high, as seen from the pressure protocol (E). At pressures beyond 150 mmHg, MscS current completely saturates and MscL currents were recorded on top of a flat MscS response. As seen from the coinciding responses to saturating pulse (D), the inactivation of MscS and MscL after 3-s stimulation is negligibly small.