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SecYEG assembles into a tetramer to form the active protein translocation channel
E H Manting1, C van Der Does, H Remigy
1Department of Microbiology, Groningen Biomolecular Sciences, Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
The EMBO Journal
|March 4, 2000
Summary
SecA protein recruits SecYEG complexes to form the active translocation channel in Escherichia coli. This translocase assembly, crucial for protein transport, comprises a SecA homodimer and four SecYEG complexes.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The Escherichia coli inner membrane utilizes a translocase system for preprotein translocation.
- This essential machinery is composed of the SecYEG integral membrane protein complex and the peripheral ATPase SecA.
Purpose of the Study:
- To elucidate the structural organization and stoichiometry of the active translocase complex.
- To understand how SecA interacts with SecYEG to form the functional translocation channel.
Main Methods:
- Functional assays were employed to assess translocase activity.
- Negative-stain electron microscopy provided structural insights.
- Scanning transmission electron microscopy determined mass and stoichiometry.
Main Results:
- SecA was shown to recruit SecYEG complexes, forming the active translocation channel.
- The active SecYEG assembly measures 10.5 nm in side length with a central cavity of approximately 5 nm.
- The translocase complex consists of a SecA homodimer associated with four SecYEG complexes.
Conclusions:
- The study reveals the precise composition of the E. coli translocase.
- This detailed structural and stoichiometric information clarifies the mechanism of protein translocation across the inner membrane.