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1.A.22.1.1
Large mechanosensitive ion channel: MscL, with a subunit size of 136 aas with 2 TMSs; it catalyzes efflux of ions (slightly cation selective), osmolytes and small proteins. Residues in the putative primary gate are present in the first TMS (Levin and Blount 2004). Protein-lipid interactions are important for gating, dependent on TMS tilting (Iscla et al., 2011b).  The carboxyl-terminal cytoplasmic helices assemble into a pentameric bundle that resembles cartilage oligomeric matrix protein, and these are required for the selective formation of the pentamer (Ando et al. 2015). Lysophospholipids can increase the size of particles that can be transported (Foo et al. 2015). 500 - 700 channels are needed for 80% survival follwing a large changes in osmotic pressure, a number of channels similar to that found in wild type E. coli cells (Chure et al. 2018). its activation threshold decreases with membrane thickness; the membrane-thickness-dependent MscL opening mainly arises from structural changes in MscL to match the altered membrane thickness by stretching (Katsuta et al. 2018). MscL can provide a route for antibiotic entry into the E. coli cell, and agonists are available to facilitate their entry (Wray et al. 2020; Zhao et al. 2020). MscL has been used to design a synthetic mechanosensitive signaling pathway in compartmentalized artificial cells (Hindley et al. 2019). Available information at the ultrastructural level on lipids tightly bound to transport proteins and the impact of altered bulk membrane lipid composition has been reviewed (Stieger et al. 2021). Competition between hydrophobic mismatch and tension may result in opening tension for MscL (Wiggins and Phillips 2004).

Accession Number:P0A742
Protein Name:Large-conductance mechanosensitive channel MscL aka B3291
Length:136
Molecular Weight:14957.00
Species:Escherichia coli [83333]
Number of TMSs:2
Location1 / Topology2 / Orientation3: Cell inner membrane1 / Multi-pass membrane protein2
Substrate ions, Osmolytes, Small proteins

Cross database links:

DIP: DIP-29827N
RefSeq: AP_004500.1    NP_417749.1   
Entrez Gene ID: 947787   
Pfam: PF01741   
BioCyc: EcoCyc:EG11180-MONOMER    ECOL168927:B3291-MONOMER   
KEGG: ecj:JW3252    eco:b3291   

Gene Ontology

GO:0016021 C:integral to membrane
GO:0005886 C:plasma membrane
GO:0008381 F:mechanically-gated ion channel activity
GO:0009992 P:cellular water homeostasis
GO:0006811 P:ion transport

References (9)

[1] “A large-conductance mechanosensitive channel in E. coli encoded by mscL alone.”  Sukharev S.I.et.al.   7511799
[2] “A merR homologue at 74 minutes on the Escherichia coli genome.”  Christie G.E.et.al.   8063098
[3] “The complete genome sequence of Escherichia coli K-12.”  Blattner F.R.et.al.   9278503
[4] “Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110.”  Hayashi K.et.al.   16738553
[5] “NAD+ binding to the Escherichia coli K(+)-uptake protein TrkA and sequence similarity between TrkA and domains of a family of dehydrogenases suggest a role for NAD+ in bacterial transport.”  Schloesser A.et.al.   8412700
[6] “Membrane topology and multimeric structure of a mechanosensitive channel protein of Escherichia coli.”  Blount P.et.al.   8890153
[7] “Structure of the MscL homolog from Mycobacterium tuberculosis: a gated mechanosensitive ion channel.”  Chang G.et.al.   9856938
[8] “Protection of Escherichia coli cells against extreme turgor by activation of MscS and MscL mechanosensitive channels: identification of genes required for MscS activity.”  Levina N.et.al.   10202137
[9] “Global topology analysis of the Escherichia coli inner membrane proteome.”  Daley D.O.et.al.   15919996
Structure:
1KYK   1KYL   1KYM   4LKU     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MSIIKEFREF AMRGNVVDLA VGVIIGAAFG KIVSSLVADI IMPPLGLLIG GIDFKQFAVT 
61:	LRDAQGDIPA VVMHYGVFIQ NVFDFLIVAF AIFMAIKLIN KLNRKKEEPA AAPAPTKEEV 
121:	LLTEIRDLLK EQNNRS