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Two nonredundant SecA homologues function in mycobacteria
M Braunstein1, A M Brown, S Kurtz
1Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA. braunste@med.unc.edu
Journal of Bacteriology
|November 22, 2001
Summary
Mycobacterium tuberculosis protein export involves two SecA proteins: SecA1 is essential, while SecA2 is nonessential and aids SecA1 in protein transport, suggesting a distinct role for SecA2.
Area of Science:
- Microbiology
- Molecular Biology
- Protein Transport
Background:
- Extracytoplasmic protein localization is crucial for mycobacterial physiology and pathogenesis.
- The Sec-dependent protein export pathway, involving SecA, is well-characterized in E. coli but unexplored in mycobacteria.
- SecA is a conserved, central component of bacterial protein export systems.
Purpose of the Study:
- To investigate the unexplored protein export systems in mycobacteria.
- To characterize the roles of two identified mycobacterial SecA homologues, SecA1 and SecA2.
Main Methods:
- Utilized an allelic-exchange strategy in Mycobacterium smegmatis.
- Conducted phenotypic analysis of a Delta secA2 mutant.
Main Results:
- Identified two SecA homologues in mycobacteria: SecA1 and SecA2.
- Demonstrated that secA1 is essential, analogous to E. coli secA.
- Showed that secA2 is nonessential and can be deleted, representing the first nonessential secA homologue.
- SecA2 assists SecA1 in exporting some proteins via the Sec pathway but is not functionally equivalent.
- SecA2 is highly conserved in mycobacteria, suggesting a specialized role.
Conclusions:
- SecA1 represents the canonical SecA protein essential for the conserved Sec pathway in mycobacteria.
- SecA2 plays a role in protein export, potentially assisting SecA1, and has a distinct, conserved function.
- The nonessential nature and conserved presence of SecA2 suggest a specific role in exporting a subset of proteins.