Oral Presentation 2014 International Biophysics Congress

Following the gating of a mechanosensitive ion channel: From patch clamp to ion mobility-mass spectrometry (#64)

Armagan Kocer 1 2 , J. P. Birkner 2 , N. Mukherjee 2 , M. D. Jose 2 , D. Yilmaz 2 , M. Walko 2 , E. Halza 2 , A. Dimitrova 2 , H. I. Ingolfsson 2
  1. Neuroscience Department, University Medical Centre Groningen, Groningen, The Netherlands
  2. Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands

Of our five senses, the molecular basis for the mechanical sensations, which involves sensing forces such as osmotic membrane stretch, vibration, touch and texture, still needs to be elucidated. The relevant force-transducing molecules, “mechano-sensitive ion channels (MSC),” have been identified1. The mechanosensitive channel of large conductance (MscL) from Escherichia coli is one of the “simplest” and the most studied MSCs. It senses membrane tension invoked by sudden hypo osmotic stress and couples it directly with large conformational changes leading to the opening of a transient, aqueous pore in the membrane2,3. Despite a large body of data and proposed gating models4-9, the inability to ‘observe’ the molecular changes occurring in mechanosensitive channels from the onset of the force has been a major limitation to describe the mechanism of mechanosensation. To this end, we studied MscL with new approaches. First, we obtained single-subunit resolution for manipulating and monitoring of MscL and showed experimentally its hydrophobic and asymmetric gating10. Next, we defined the pore diameter of MscL at the very first subopen stage11. We had control over the channel gating by interfering with its interaction with the lipid bilayer and showed that MscL from different homologues reacts differently to the global and local changes in the lipid bilayer properties1 2 . By using light as a trigger for channel activation, we followed the conformational changes at early stages of gating by EPR. Finally, we could show global conformation changes of the channel using ion mobility mass spectroscopy.

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