Mechanosensitive Channel of Large Conductance (MscL)
Model of Channel Opening
Theoretical models of the (initial scene), , and forms of the channel have been generated based on data from electron paramagnetic resonance spectroscopy, using mutant forms of the protein with spin labels attached to engineered cysteine amino acids in the transmembrane segments.
|2oar, resolution 3.50Å ()|
Mechanosensitive ion channels play a critical role in transducing physical stresses at the cell membrane into an electrochemical response. The MscL family of large-conductance mechanosensitive channels is widely distributed among prokaryotes and may participate in the regulation of osmotic pressure changes within the cell. In an effort to better understand the structural basis for the function of these channels, the structure of the MscL homolog from Mycobacterium tuberculosis was determined by x-ray crystallography to 3.5 angstroms resolution. This channel is organized as a homopentamer, with each subunit containing two transmembrane alpha helices and a third cytoplasmic alpha helix. From the extracellular side, a water-filled opening approximately 18 angstroms in diameter leads into a pore lined with hydrophilic residues which narrows at the cytoplasmic side to an occluded hydrophobic apex that may act as the channel gate. This structure may serve as a model for other mechanosensitive channels, as well as the broader class of pentameric ligand-gated ion channels exemplified by the nicotinic acetylcholine receptor.
Structure of the MscL homolog from Mycobacterium tuberculosis: a gated mechanosensitive ion channel., Chang G, Spencer RH, Lee AT, Barclay MT, Rees DC, Science. 1998 Dec 18;282(5397):2220-6. PMID:9856938
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
Many structural features of a related channel, MscS, including animated morphs of opening an closing, are illustrated at Mechanosensitive channels: opening and closing.
References and Notes
- ↑ The theoretical models were deposited in the PDB (before it stopped accepting theoretical models) as 1kyk, 1kyl, and 1kym.
- ↑ Open channel structure of MscL and the gating mechanism of mechanosensitive channels. Perozo, E, Cortes DM, Sompornpisut, P, Kloda, A, Martinac, B. Nature 2002, 418, 942-948. PMID:12198539
- ↑ Structure of the MscL homolog from Mycobacterium tuberculosis: a gated mechanosensitive ion channel., Chang G, Spencer RH, Lee AT, Barclay MT, Rees DC, Science. 1998 Dec 18;282(5397):2220-6. PMID:9856938
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