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Mechanosensitive channels of Escherichia coli: the MscL gene, protein, and activitiesAlthough mechanosensory responses are ubiquitous and diverse, the molecular bases of mechanosensation in most cases remain mysterious MscL, a mechanosensitive channel of large conductance of Escherichia coli and its bacterial homologues are the first and currently only channel molecules shown to directly sense mechanical stretch of the membrane. In response to the tension conveyed via the lipid bilayer, MscL increases its open probability by several orders of magnitude. In the present review we describe the identification, cloning, and first sets of biophysical and structural data on this simplest mechanosensory molecule. We discovered a 2.5-ns mechanosensitive conductance in giant E. coli spheroplasts. Using chromatographies to enrich the target and patch clamp to assay the channel activity in liposome-reconstituted fractions, we identified the MscL protein and cloned the mscL gene. MscL comprises 136 amino acid residues (15 kDa), with two highly hydrophobic regions, and resides in the inner membrane of the bacterium. PhoA-fusion experiments indicate that the protein spans the membrane twice with both termini in the cytoplasm. Spectroscopic techniques show that it is highly helical. Expression of MscL tandems and covalent cross-linking suggest that the active channel complex is a homo-hexamer. We have identified several residues, which when deleted or substituted, affect channel kinetics or mechanosensitivity. Although unique when discovered, highly conserved MscL homologues in both gram-negative and gram-positive bacteria have been found, suggesting their ubiquitous importance among bacteria.
Document ID
20040173058
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Sukharev, S. I.
(University of Wisconsin Madison 53706, United States)
Blount, P.
Martinac, B.
Kung, C.
Date Acquired
August 22, 2013
Publication Date
January 1, 1997
Publication Information
Publication: Annual review of physiology
Volume: 59
ISSN: 0066-4278
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: GM47856
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Review
NASA Discipline Cell Biology
Review, Tutorial

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