Chimeras Reveal a Single Lipid-Interface Residue that Controls MscL Channel Kinetics as well as Mechanosensitivity

Dalian Zhong,Li-Min Yang,Paul Blount

doi:10.1016/j.celrep.2013.01.018

Dalian Zhong, Li-Min Yang + Show 1 more

Open Access

https://doi.org/10.1016/j.celrep.2013.01.018

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Abstract

MscL, the highly conserved bacterial mechanosensitive channel of large conductance, serves as an osmotic "emergency release valve," is among the best-studied mechanosensors, and is a paradigm of how a channel senses and responds to membrane tension. Although all homologs tested thus far encode channel activity, many show functional differences. We tested Escherichia coli and Staphylococcus aureus chimeras and found that the periplasmic region of the protein, particularly E.coli I49 and the equivalent S.aureus F47 at the periplasmic lipid-aqueous interface of the first transmembrane domain, drastically influences both the open dwell time and the threshold of channel opening. One mutant shows a severe hysteresis, confirming the importance of this residue in determining the energy barriers for channel gating. We propose that this site acts similarly to a spring for a clasp knife, adjusting the resistance for obtaining and stabilizing an open or closed channel structure.

Highlights

The ability to detect mechanical forces is at the basis of the senses of touch, hearing and balance and cardiovascular and osmotic regulation
The mechanosensitive channel of large conductance (MscL) is a bacterial channel located in the cytoplasmic membrane that is gated by membrane tension (Blount et al, 2008a; Blount et al, 2007; Blount et al, 2008b; Booth and Blount, 2012)
The periplasmic region of the channel plays a major role in defining channel kinetics In an attempt to correlate channel kinetics with specific regions of the protein, numerous chimeras of the Eco- and Sa-MscL channel proteins were generated

Summary

Introduction

The ability to detect mechanical forces is at the basis of the senses of touch, hearing and balance and cardiovascular and osmotic regulation. The best-studied mechanosensitive channels are from bacteria, and because relatively little is known of mechanosensors from higher organisms, these channels are a model for how a protein can sense and respond to mechanical forces. The MscL family is highly conserved and has a simple structural organization (Balleza and Gomez-Lagunas, 2009; Pivetti et al, 2003). This exaggerated response and simple construction lends itself as a paradigm for how MS channels, in general, can sense and respond to membrane stretch

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