Biomolecular Stress-Sensitive Gauges: Surface-Mediated Immobilization of Mechanosensitive Membrane Protein.

摘要

Stress-sensitive proteins, which serve as pressure relief valves in the cell membrane, are considered as a promising model of biomolecular gauges. Studies of a mechanosensitive protein of large conductance (MscL) had shown that a dramatic change in the protein conformation is caused by membrane tension rather than the ion concentration gradient. Recent structural studies of such membrane channel proteins suggested an architecture with a large pore opening under mechanical stresses. The elastic barrel composed of highly tilted helices acts as a tension sensor and was responsible for a large iris -like expansion and flattening of the protein triggered by local stresses in the cell membrane. A variation of the lateral pressure within the lipid bilayer, asymmetric bending, and, to lesser extent, membrane thinning were found to be the main driving forces for pore opening. The transition from a closed state to a closed-expanded state occurs initially as a result of a gradual increase in helical tilt angle. Under further membrane tension, the helices move away and dock to the rest of the open structure, resulting in a flat structure with a large central opening. However, to date, no attempts have been undertaken to immobilize these proteins in a controlled open/close state on a microelectronic- related surface as an initial step toward designing biomolecular gauges. An open structure of this membrane protein causes a significant challenge in its immobilization because it is prone to collapse on a solid surface. Here, we report on the design of protein-organic surface nanostructures containing stress-sensitive membrane protein, MscL, from Salmonella typhymurium. We designed supported organic monolayers (alkylsilane self-assembled (SAM) and lipid Langmuir- Blodgett (LB)) with different packing densities and surface tensions, which can be directly used for membrane protein immobilization (see Supporting Information).