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Folding with and without encapsulation by cis- and trans-only GroEL-GroES complexes
George W Farr1, Wayne A Fenton, Tapan K Chaudhuri
1Howard Hughes Medical Institute and Department of Genetics, Yale School of Medicine, Boyer Center, 295 Congress Avenue, New Haven, CT 06510, USA.
The EMBO Journal
|July 4, 2003
Summary
The GroEL-GroES chaperonin system can fold proteins using a trans mechanism, where GroES binds to the opposite ring. This method is productive for large proteins like aconitase and smaller substrates, though cis encapsulation is more efficient.
Area of Science:
- Molecular Biology
- Protein Folding
- Chaperone Proteins
Background:
- The GroEL-GroES chaperonin system facilitates protein folding.
- A cis mechanism, involving encapsulation within GroES, is well-established.
- A trans mechanism was recently proposed for large proteins like aconitase.
Purpose of the Study:
- To further evaluate the trans mechanism of GroEL-GroES-mediated protein folding.
- To investigate the efficiency of the trans mechanism for various substrates.
- To assess the in vivo functionality of a trans-only GroEL-GroES complex.
Main Methods:
- Utilized trans-only GroEL-GroES complexes with tethered GroES.
- Assessed in vitro folding kinetics of aconitase, Rubisco, and malate dehydrogenase.
- Evaluated in vivo protein folding by rescuing a GroEL-deficient strain.
Main Results:
- Trans-only complexes folded aconitase in vitro with kinetics identical to cis GroEL-GroES.
- Trans-only complexes folded smaller substrates (Rubisco, malate dehydrogenase) slower than cis.
- In vivo, trans-only complexes partially rescued GroEL deficiency, yielding smaller colonies.
Conclusions:
- A trans mechanism is a generally productive pathway for GroEL-GroES-mediated folding.
- The trans mechanism is crucial for folding large proteins that cannot be encapsulated.
- Cis encapsulation remains the more efficient folding mechanism when substrate size permits.