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Translocase-bound SecA is largely shielded from the phospholipid acyl chains
F van Voorst1, C van der Does, J Brunner
1Department of Biochemistry of Membranes, Institute Biomembranes, Utrecht University, The Netherlands. F.vanvoorst@chem.ruu.nl
Biochemistry
|September 2, 1998
Summary
SecA ATPase interaction with the SecYEG translocase in E. coli is modulated by membrane lipids. Excess SecYEG shields SecA from lipids, suggesting distinct membrane-associated SecA pools.
Area of Science:
- Cellular Biology
- Protein Transport Mechanisms
- Membrane Protein Complexes
Background:
- Protein translocation in Escherichia coli relies on the SecA ATPase and the SecYEG membrane complex.
- SecA activity and protein movement across membranes necessitate negatively charged lipids.
Purpose of the Study:
- To investigate the lipid accessibility of SecA when bound to the translocase.
- To determine how the SecYEG complex influences SecA's association with membrane lipids.
Main Methods:
- Utilized photoactivatable phospholipids to probe SecA's lipid accessibility.
- Examined SecA-lipid interactions in vesicles with and without excess SecYEG complex.
Main Results:
- SecA bound to negatively charged lipid vesicles showed significant accessibility to photoactivatable phospholipids.
- An excess of SecYEG complex markedly decreased lipid-accessible SecA, regardless of SecA's nucleotide-bound state.
Conclusions:
- SecA associated with the SecYEG complex is largely shielded from membrane acyl chains.
- Evidence suggests two distinct populations of membrane-bound SecA with varying lipid interactions exist.