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Dynamics of protein-protein interactions at the MscL periplasmic-lipid interface

Dalian Zhong1, Li-Min Yang1, Paul Blount1

  • 1Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, Texas.

Biophysical Journal
|January 28, 2014
PubMed

Insights

Bacterial mechanosensitive channels (MscL) act as emergency release valves. Introducing cysteine mutations at key sites reduced channel open time, suggesting structural rearrangements during gating.

Area of Science:

  • Biophysics
  • Molecular Biology
  • Cell Biology

Background:

  • Mechanosensitive channels of large conductance (MscL) are crucial bacterial mechanosensors.
  • MscL functions as a cellular emergency release valve, preventing lysis under osmotic stress.
  • Specific residues in the MscL periplasmic region significantly influence channel gating kinetics and mechanosensitivity.

Purpose of the Study:

  • To investigate the role of specific periplasmic residues in MscL gating dynamics.
  • To explore the structural implications of disulfide bond formation at these critical sites.
  • To understand the protein-protein interactions and conformational changes underlying MscL function.

Main Methods:

  • Site-directed mutagenesis to introduce cysteine residues at key MscL periplasmic sites.
  • Disulfide bond formation assays to probe protein structure and interactions.
  • Electrophysiological recordings to measure channel open dwell time and kinetics.

Main Results:

  • Cysteine mutations at the TM1/periplasmic loop interface (e.g., F47 in S. aureus MscL) formed disulfide bridges.
  • Disulfide bond formation significantly decreased the channel's open dwell time, leading to faster kinetics.
  • Disulfide trapping of other periplasmic loop residues also resulted in rapid channel gating, indicating conformational constraints.

Conclusions:

  • The periplasmic region of MscL undergoes structural rearrangements during normal gating.
  • Disulfide bond formation within the periplasmic loop can lock the channel in a transition state.
  • Locking MscL in a transition state reduces the stability of the open channel conformation, impacting its function as a mechanosensor.

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