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Atomic model of the E. coli membrane-bound protein translocation complex SecYEG
Mihnea Bostina1, Brigitte Mohsin, Werner Kühlbrandt
1Department of Structural Biology, Max-Planck-Institute of Biophysics, 60439 Frankfurt am Main, Germany.
Journal of Molecular Biology
|September 13, 2005
Summary
The SecYEG complex in E. coli forms a protein-conducting channel. Structural analysis reveals the dimer interface may activate assembly, with movements in the substrate-binding site and plug domain influencing channel gating.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- The Sec complex is essential for protein transport across membranes.
- SecYEG in Escherichia coli functions as an oligomer, but the monomer forms the channel.
- Previous models suggested monomeric activity, but oligomeric structures are observed.
Purpose of the Study:
- To determine the structure of the membrane-bound SecYEG dimer.
- To understand the structural basis of SecYEG channel gating and activation.
Main Methods:
- Homology modeling using Methanococcus jannaschii SecYEbeta structure.
- Fitting homology model to an 8Å electron microscopy map of E. coli SecYEG.
- Structural analysis of the membrane-bound dimer.
Main Results:
- A structural model of the membrane-bound SecYEG dimer was determined.
- The substrate-binding site showed slight opening, and the plug domain moved outward.
- These movements suggest the channel remains closed but poised for gating.
Conclusions:
- Dimer interface contacts in the lipid bilayer may activate SecYEG assembly.
- Substrate binding and release likely involve partner proteins and plug domain displacement.
- The determined structure provides insights into the dynamic mechanism of protein translocation.
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