3HZQ image
Deposition Date 2009-06-24
Release Date 2009-08-25
Last Version Date 2024-02-21
Entry Detail
PDB ID:
3HZQ
Title:
Structure of a tetrameric MscL in an expanded intermediate state
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
3.82 Å
R-Value Free:
0.31
R-Value Work:
0.29
R-Value Observed:
0.29
Space Group:
I 4 3 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Large-conductance mechanosensitive channel
Gene (Uniprot):mscL
Mutations:S32C
Chain IDs:A
Chain Length:114
Number of Molecules:1
Biological Source:Staphylococcus aureus subsp. aureus MW2
Ligand Molecules
Primary Citation
Structure of a tetrameric MscL in an expanded intermediate state.
Nature 461 120 124 (2009)
PMID: 19701184 DOI: 10.1038/nature08277

Abstact

The ability of cells to sense and respond to mechanical force underlies diverse processes such as touch and hearing in animals, gravitropism in plants, and bacterial osmoregulation. In bacteria, mechanosensation is mediated by the mechanosensitive channels of large (MscL), small (MscS), potassium-dependent (MscK) and mini (MscM) conductances. These channels act as 'emergency relief valves' protecting bacteria from lysis upon acute osmotic down-shock. Among them, MscL has been intensively studied since the original identification and characterization 15 years ago. MscL is reversibly and directly gated by changes in membrane tension. In the open state, MscL forms a non-selective 3 nS conductance channel which gates at tensions close to the lytic limit of the bacterial membrane. An earlier crystal structure at 3.5 A resolution of a pentameric MscL from Mycobacterium tuberculosis represents a closed-state or non-conducting conformation. MscL has a complex gating behaviour; it exhibits several intermediates between the closed and open states, including one putative non-conductive expanded state and at least three sub-conducting states. Although our understanding of the closed and open states of MscL has been increasing, little is known about the structures of the intermediate states despite their importance in elucidating the complete gating process of MscL. Here we present the crystal structure of a carboxy-terminal truncation mutant (Delta95-120) of MscL from Staphylococcus aureus (SaMscL(CDelta26)) at 3.8 A resolution. Notably, SaMscL(CDelta26) forms a tetrameric channel with both transmembrane helices tilted away from the membrane normal at angles close to that inferred for the open state, probably corresponding to a non-conductive but partially expanded intermediate state.

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