Mechanosensation underlies fundamental biological processes, including osmoregulation in microbes, touch and hearing in animals, and gravitropism and turgor pressure sensing in plants. and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These 84625-61-6 manufacture results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands. Mechanosensitive channels (MSCs) are a fundamental class of membrane proteins capable of detecting and responding to mechanical stimuli originating from external Mouse monoclonal to FOXP3 or internal environments. They are widespread in animals, plants, fungi, bacteria, and archaea, with crucial functions in adaptation and sensation (1, 2). MSCs may share a common principle enabling them to transduce mechanical forces into electrochemical signals (3), although the divergent evolution of mechanosensitive channels has led to highly diverse protein sequences and different overall architectures among them (4). In animals, the sensations of touch and hearing require the functions 84625-61-6 manufacture of MSCs (2). Malfunctions of MSCs are associated with diseases like cardiac arrhythmias, hypertension, neuronal and muscle degeneration, polycystic kidney disease, etc. (5). In plants, the MSCs protect plastids from hypo-osmotic stress of the cytoplasm (6). In bacteria, they fulfill functional roles as emergency valves and protect cells from acute hypotonic osmotic stress in the environments (7, 8). When challenged by acute osmotic downshock, cells lacking large-conductance and small-conductance MSCs (MscL and MscS) will have their membrane ruptured, resulting in cell lysis (9). As one of the two main classes of microbial mechanosensitive channels (MscL and MscS; the MscS family includes MscS, MscK, MscM, etc.), MscL has the largest conductance (at 3 nS) at the fully open state and gates at the highest pressure threshold near the lytic limit of the cell membrane (10). Since it was originally identified in 1994 (11), MscL has 84625-61-6 manufacture been well recognized as a model system for studying the molecular basis of mechanosensation through electrophysiology, biochemistry, genetics, structural biology, and molecular dynamic simulation approaches (12). Pioneering works demonstrated that MscL can be converted into a light-activated nanovalve useful for the triggered release of compounds in liposomes (13C15). Recent studies suggest that the open pore of MscL permits entry of streptomycin and could potentially serve as a target for antimicrobial agents (16, 17). The gating process of MscL involves large conformational changes when it transits from the closed state to the open state through several intermediates (18). In the open state, MscL 84625-61-6 manufacture dilates its central pore to 30 ? wide and becomes permeable to water, ions, metabolites, and even small proteins (19C21). To describe the gating-related structural changes of MscL, an iris-like open-state model was proposed based on computational modeling (22) and disulfide cross-linking data (23). This model was verified and revised by further studies through electron paramagnetic resonance spectroscopy (24) and an electrostatic repulsion test (25). More recently, a study through the native ion mobilityCmass spectrometry demonstrated that MscL has the inherent structural flexibility to achieve large global structural changes in the absence of a lipid.