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Intracellular localization of a group II chaperonin indicates a membrane-related function.
Jonathan D Trent1, Hiromi K Kagawa, Chad D Paavola
1National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035, USA. jonathan.d.trent@nasa.gov
Summary
Group II chaperonins, or rosettasomes, in Sulfolobus shibatae associate with the cell membrane. Their increased abundance after heat shock correlates with decreased membrane permeability, suggesting a structural role.
Area of Science:
- Microbiology
- Biochemistry
- Cell Biology
Background:
- Chaperonins are typically cytoplasmic protein folding machinery.
- Group II chaperonins, known as rosettasomes, were investigated in the hyperthermophilic archaeon Sulfolobus shibatae.
Purpose of the Study:
- To investigate the cellular localization and function of group II chaperonins (rosettasomes) in Sulfolobus shibatae.
- To determine the role of rosettasomes in cellular response to heat stress and membrane integrity.
Main Methods:
- Immunofluorescence microscopy and immunogold electron microscopy to determine rosettasome localization.
- Heat shock experiments with and without azetidine 2-carboxylic acid to assess membrane permeability.
- Liposome binding assays and differential scanning calorimetry to analyze rosettasome-lipid interactions.
Main Results:
- Rosettasomes were found to be membrane-associated, not cytoplasmic, in S. shibatae.
- Increased rosettasome abundance after heat shock correlated with decreased membrane permeability at high temperatures.
- Functional protein synthesis, not lipid composition changes, influenced heat-induced membrane permeability.
Conclusions:
- Group II chaperonins (rosettasomes) in S. shibatae likely function as a structural component of the cell membrane.
- Rosettasomes contribute to maintaining membrane integrity under heat stress conditions.
- The membrane association and abundance changes suggest a role beyond traditional cytoplasmic protein folding.