Biomolecular stress-sensitive gauges: surface-mediated immobilization of mechanosensitive membrane protein.

We report the observation of structural reorganizations associated with unique, stress-assisted gating of mechanosensitive (MscL) membrane protein on a silicon surface modified with alkyl-terminated monolayers. We observed that the shape of MscL membrane proteins changed dramatically depending upon the packing density of alkyl tails and the surface tension of the supporting organic layer. High-resolution atomic force microscopy confirmed a transition from an elongated, prolate shape of MscL molecules within a monolayer with low surface tension to a flattened, oblate shape with a wide central opening within a monolayer with high surface tension. These observations are consistent with the conformation reorganizations associated with the two-stage, "iris"-like expansion proposed for the gating of the MscL molecules.