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Covalently dimerized SecA is functional in protein translocation
Jeanine de Keyzer1, Eli O van der Sluis, Robin E J Spelbrink
1Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Materials and Science Centre Plus, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
The Journal of Biological Chemistry
|August 24, 2005
Summary
The SecA dimer
Area of Science:
- Molecular biology
- Protein transport
- Cellular machinery
Background:
- SecA is an ATPase essential for protein transport across the E. coli cytoplasmic membrane.
- SecA's oligomeric state during translocation is debated, impacting our understanding of this vital cellular process.
Purpose of the Study:
- To investigate the necessity of SecA dimer dissociation for protein translocation.
- To elucidate the role of oligomeric changes in SecA function during membrane transport.
Main Methods:
- Formation of a non-dissociable SecA dimer via disulfide bond cross-linking.
- Assessing SecA dimer interaction with the SecYEG complex and SecB binding.
- Evaluating the activity of cross-linked SecA in protein translocation assays.
Main Results:
- Cross-linked SecA dimer binds SecYEG with similar stoichiometry to wild-type SecA.
- SecA cross-linking reversibly disrupts SecB binding but does not impair activity without SecB.
- SecYEG binding stabilizes a dimeric SecA state resistant to SDS.
Conclusions:
- SecA dimer dissociation is not essential for protein translocation across the E. coli membrane.
- The SecA dimer can actively participate in protein transport, challenging previous models.