Desensitization, Inactivation, and the tension-proof safety mechanism of inactivated MscS

Bacterial energetics, which relies on the electrochemical proton gradient across the inner membrane as an intermediary, conflicts with the presence of a dense population of highly conductive mechano-activated channels in the same cytoplasmic membrane, which must be proton-tight. Moreover, the tension activation threshold for the common MscS channel is low and can be easily exceeded by fluctuations in the concentrations of internal or external osmolytes. In this paper, we describe the important adaptive inactivation of MscS at tensions near its activation threshold, and specifically, the complete resistance of inactivated MscS to opening at any tension. The data show another layer of tight regulation of MscS residing in the energy-coupling membranes.