A large-conductance mechanosensitive channel in E. coli encoded by mscL alone

Area of Science:

• Molecular Biology
• Cell Biology
• Biophysics

Background:

• Cellular organisms sense mechanical stimuli, but the underlying molecules remain unidentified.
• Mechanosensitive channels, activated by membrane stretch, are potential candidates for these sensory roles.
• Escherichia coli exhibits mechanosensitive channels, including MscL (large conductance) and MscS (small conductance), potentially involved in osmoregulation.

Purpose of the Study:

• To identify the protein responsible for the large conductance mechanosensitive channel (MscL) activity in Escherichia coli.
• To characterize the MscL channel and its gene (mscL).

Main Methods:

• Solubilization and fractionation of Escherichia coli envelope.
• In vitro reconstitution of MscL channel activity.
• Gene cloning of mscL.
• Insertional gene disruption and re-expression studies.
• Cell-free expression system analysis.

Main Results:

• MscL channel activity was successfully reconstituted in vitro and traced to a specific small protein.
• The gene encoding MscL (mscL) was cloned.
• Disruption of mscL abolished channel activity, while re-expression restored it.
• MscL activity was confirmed using a cell-free expression system.
• The mscL gene predicts a unique 136-amino acid protein with a hydrophobic core.

Conclusions:

• The MscL protein is identified as the molecular basis for the large conductance mechanosensitive channel in Escherichia coli.
• MscL plays a significant role in cellular mechanosensation and potentially osmoregulation.
• The unique structure of MscL distinguishes it from other known membrane proteins.