Single molecule FRET reveals pore size and opening mechanism of a mechano-sensitive ion channel
Helix-tilt Model, Pore Diameter, MscL opening
The mechanosensitive channel of large conductance, which serves as a model system for mechanosensitive channels, has previously been crystallized in the closed form, but not in the open form. Ensemble measurements and electrophysiological sieving experiments show that the open-diameter of the channel pore is >25 Å, but the exact size and whether the conformational change follows a helix-tilt or barrel-stave model are unclear. Here we report measurements of the distance changes on liposome-reconstituted MscL transmembrane α-helices, using a ‘virtual sorting’ single-molecule fluorescence energy transfer. We observed directly that the channel opens via the helix-tilt model and the open pore reaches 2.8 nm in diameter. In addition, based on the measurements, we developed a molecular dynamics model of the channel structure in the open state which confirms our direct observations.
Wang, Y., Liu, Y., DeBerg, H. A., Nomura, T., Hoffman, M. T., Rohde, P. R., Schulten, K., Martinac, B., & Selvin, P. R. (2014). Single molecule FRET reveals pore size and opening mechanism of a mechano-sensitive ion channel. Physics Faculty Publications and Presentations., 3, e01834. https://doi.org/https://doi.org/10.7554/eLife.01834.001