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Updated: Oct 31, 2025

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Published on: December 17, 2013
Control of membrane barrier during bacterial type-III protein secretion
Svenja Hüsing1,2, Manuel Halte1, Ulf van Look1,2
1Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany.
Bacterial secretion systems use a methionine gasket (M-gasket) to rapidly export proteins while blocking small molecules. This M-gasket, along with other structures, maintains membrane integrity during high-speed protein transport.
Area of Science:
- Microbiology
- Molecular Biology
- Biophysics
Background:
- Type-III secretion systems (T3SSs) and injectisomes translocate proteins at high speeds.
- Maintaining membrane integrity during rapid protein export is a key challenge.
Purpose of the Study:
- To investigate the mechanism by which T3SSs achieve rapid protein translocation while preventing small molecule leakage.
- To identify the structural components responsible for maintaining membrane integrity during secretion.
Main Methods:
- Mutational analysis of T3SS components.
- Evolutionary analysis of conserved residues.
- Investigating the role of methionine residues in the T3SS channel.
Main Results:
- Identified a conserved ensemble of methionine residues forming a deformable gasket (M-gasket) at the cytoplasmic side of the T3SS channel.
- Demonstrated that the M-gasket is crucial for preserving the membrane barrier and accommodating conformational changes during secretion.
- Showed that the M-gasket cooperates with a plug domain (R-plug) and salt-bridges to maintain secretion pore stability.
Conclusions:
- The M-gasket, R-plug, and salt-bridge network represent a conserved mechanism for maintaining membrane integrity during high-speed protein translocation in T3SSs.
- The unique physicochemical properties of the M-gasket are essential for efficient and regulated protein secretion.
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