FIGURE 1.

Activation of MscL by transbilayer pressure gradients. (A) Patch-clamp recordings of channels at −20 mV (pipette positive) from spheroplasts expressing the wild-type MscL after induction with IPTG (1 mM, 30 min). A total of 52 channels were observed at the pressure close to saturating. (B) MscL activities recorded without IPTG induction. Five channels are observed in this particular experiment. The pressure traces measured in mm Hg are shown below each current trace. The points of half-maximal activation of MscS and first openings of MscL are indicated by arrows and asterisks, respectively. Using pressure that elicits half-maximal activation of MscS, p_1/2^MscS (which corresponds to tension of 5.5 dyn/cm), the pressure scale was converted into the scale of tensions. Inset represents the distribution of radii of curvature (r) calculated from the law of Laplace in 21 patches sampled with standard 5 MOhm pipettes.