The bacterial mechanosensitive channel of large conductance, MscL, is an important model system to study the conversion of mechanical stimuli into chemical signals due to its simple structure and small size. While we know a great deal about the conditions required for gating of MscL, i.e., membrane tension, lipid composition, temperature, etc., as well as the protein residues critical for gating, we still do not understand how forces are transduced to the channel. In other words, the mechanism by which membrane lipids exert forces on the protein surface and induce gating remains unknown. We recently showed that a cluster of four charged residues on the cytoplasmic side of <i>Mycobacterium tuberculosis</i> MscL, K3, K6, K99, and K100, experience strong forces during membrane stretch as observed in traction plots obtained from 3D local stress calculations of molecular dynamics (MD) simulations. We also showed that the interaction between these positively charged lysines and negatively charged lipid phosphates is strong enough to actuate the channel in steered MD simulations where the tails of lipids associated with the charged cluster are pulled radially away from the center of mass of the protein. New preliminary results indicate that these lysines, in particular K3 and K6, contribute significantly to the total number of hydrogen bonds and total interaction energy between the protein and cytoplasmic lipids as shown by different simulated MscL mutants (K3T/K6T and K3T/K6T/K99T/K100T). Local stress calculations of the wild-type and mutated channels also show significant differences in the distribution of forces on the surface of the protein. Together with experimental mutation data that shows that replacement or deletion of amino acids in the N-terminal S1 domain (residues 1-11) on the cytoplasmic side leads to partial or complete loss of function, our results provide a path to understand the force transduction mechanism in MscL.<br/>

Force transduction and anchoring of the mechanosensitive channel MscL to lipid membrane through charged interactions

256th National Meeting (2018)

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