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Published on: November 12, 2012
Functional overlap but lack of complete cross-complementation of Streptococcus mutans and Escherichia coli YidC
Yuxia Dong1, Sara R Palmer, Adnan Hasona
1Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Abstract:
Oxa/YidC/Alb family proteins are chaperones involved in membrane protein insertion and assembly. Streptococcus mutans has two YidC paralogs. Elimination of yidC2, but not yidC1, results in stress sensitivity with decreased membrane-associated F(1)F(o) ATPase activity and an inability to initiate growth at low pH or high salt concentrations (A. Hasona, P. J. Crowley, C. M. Levesque, R. W. Mair, D. G. Cvitkovitch, A. S. Bleiweis, and L. J. Brady, Proc. Natl. Acad. Sci. USA 102:17466-17471, 2005). We now show that Escherichia coli YidC complements for acid tolerance, and partially for salt tolerance, in S. mutans lacking yidC2 and that S. mutans YidC1 or YidC2 complements growth in liquid medium, restores the proton motive force, and functions to assemble the F(1)F(o) ATPase in a previously engineered E. coli YidC depletion strain (J. C. Samuelson, M. Chen, F. Jiang, I. Moller, M. Wiedmann, A. Kuhn, G. J. Phillips, and R. E. Dalbey, Nature 406:637-641, 2000). Both YidC1 and YidC2 also promote membrane insertion of known YidC substrates in E. coli; however, complete membrane integrity is not fully replicated, as evidenced by induction of phage shock protein A. While both function to rescue E. coli growth in broth, a different result is observed on agar plates: growth of the YidC depletion strain is largely restored by 247YidC2, a hybrid S. mutans YidC2 fused to the YidC targeting region, but not by a similar chimera, 247YidC1, nor by YidC1 or YidC2. Simultaneous expression of YidC1 and YidC2 improves complementation on plates. This study demonstrates functional redundancy between YidC orthologs in gram-negative and gram-positive organisms but also highlights differences in their activity depending on growth conditions and species background, suggesting that the complete functional spectrum of each is optimized for the specific bacteria and environment in which they reside.
Insights
This study shows that bacterial YidC chaperones have overlapping functions in membrane protein assembly and stress tolerance. While both YidC1 and YidC2 from Streptococcus mutans can function in E. coli, their effectiveness varies with growth conditions and specific protein constructs.
Area of Science:
- Molecular Biology
- Microbiology
- Protein Biochemistry
Background:
- Oxa/YidC/Alb proteins are essential chaperones for membrane protein insertion and assembly.
- Streptococcus mutans possesses two YidC paralogs, YidC1 and YidC2, with YidC2 being crucial for stress tolerance and F(1)F(o) ATPase activity.
- Previous work established the role of E. coli YidC in complementing E. coli YidC depletion strains.
Purpose of the Study:
- To investigate the functional complementation of Streptococcus mutans YidC paralogs in Escherichia coli.
- To determine the ability of S. mutans YidC1 and YidC2 to restore membrane protein assembly, proton motive force, and stress tolerance in E. coli.
- To explore the species-specific and condition-dependent activities of YidC orthologs.
Main Methods:
- Complementation assays using engineered Escherichia coli YidC depletion strains.
- Assessment of acid and salt tolerance in Streptococcus mutans lacking yidC2.
- Analysis of F(1)F(o) ATPase assembly, proton motive force, and membrane insertion of known YidC substrates.
- Construction and testing of chimeric YidC proteins (247YidC1 and 247YidC2).
Main Results:
- Escherichia coli YidC partially complements acid and salt tolerance in S. mutans lacking yidC2.
- Streptococcus mutans YidC1 and YidC2 restore growth, proton motive force, and F(1)F(o) ATPase assembly in E. coli YidC depletion strains.
- Both S. mutans YidC1 and YidC2 promote membrane insertion of substrates in E. coli, but complete membrane integrity is not restored.
- A hybrid protein, 247YidC2, but not 247YidC1, significantly restores growth on agar plates, while simultaneous expression of YidC1 and YidC2 enhances complementation.
Conclusions:
- YidC orthologs exhibit functional redundancy across Gram-negative and Gram-positive bacteria.
- The functional spectrum of YidC proteins is influenced by species background and environmental conditions.
- Specific domains or interactions may dictate the efficiency of YidC orthologs in different bacterial contexts and growth media.
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