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The carboxyl-terminal region is essential for Sec-A dimerization
M Hirano1, S Matsuyama, H Tokuda
1Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Biochemical and Biophysical Research Communications
|December 4, 1996
Summary
The SecA protein
Area of Science:
- Biochemistry
- Molecular Biology
Background:
- SecA protein is essential for bacterial protein secretion.
- SecA functions as a dimer and binds ATP.
- The specific region responsible for SecA dimerization is not fully understood.
Purpose of the Study:
- To identify the minimal region of SecA protein essential for its physiological dimerization.
- To investigate the role of specific domains and cysteine residues in SecA dimerization and activity.
Main Methods:
- Size exclusion chromatography
- Chemical cross-linking analysis
- Analysis of truncated SecA derivatives (N95, N76, N66, C53, C28)
- ATP binding and hydrolysis assays
Main Results:
- The region 662-831 of SecA is essential for physiological dimer formation.
- N95 derivative retained SecA activity and dimerized, indicating carboxyl-terminal cysteines are dispensable for dimerization.
- Monomeric N76 could bind ATP, but ATP hydrolysis rate was reduced, suggesting dimerization is not required for ATP binding but affects hydrolysis.
- C28 formed dimers and oligomers, while C53 formed dimers, suggesting the 438-661 region influences disulfide bond formation.
Conclusions:
- The 662-831 region of SecA is critical for its dimerization.
- SecA dimerization is not a prerequisite for ATP binding but influences ATP hydrolysis.
- Specific regions of SecA regulate its oligomeric state and potentially its function in protein translocation.