Fig. 3.

Opening of MscL observed by IM-MS. (A) Charge-induced opening of MscL is reversible. The shift and dispersity of the collision cross-section observed for the 16+ charge state of G22C₅ MscL (black) upon binding of MTSET indicates opening of the channel (yellow). After adding DTT to the same sample, thus removing the positively charged MTSET from the pore lining, the channel returns to its closed state again (red). (B) Increasing the number of MTSET-labeled cysteines in the pore lining allows MscL to occupy more extended conformations. Reported collision cross-sections are corrected for the different compositions of the purification tags of the heteropentamers of MscL.