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Free human mitochondrial GrpE is a symmetric dimer in solution
Júlio C Borges1, Hannes Fischer, Aldo F Craievich
1Centro de Biologia Molecular Estrutural, Laboratório Nacional de Luz Sincroton, and Departmento de Bioquímica, Instituto de Biologia, UNICAMP, Campinas, São Paulo 13084-971, Brazil.
The Journal of Biological Chemistry
|July 4, 2003
Summary
Human mitochondrial GrpE, a protein folding co-chaperone, was characterized. Unlike prokaryotic GrpE, human GrpE forms a symmetric dimer in solution, crucial for understanding its function.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- The Hsp70 system is vital for protein folding, with GrpE acting as an essential co-chaperone.
- Understanding the structure-function relationships of GrpE homologs across different organisms is important.
Purpose of the Study:
- To clone, produce, and structurally characterize recombinant human mitochondrial GrpE.
- To investigate the conformational properties and quaternary structure of human GrpE in solution.
Main Methods:
- Circular dichroism (CD) spectroscopy for folding and thermal unfolding studies.
- Differential scanning calorimetry (DSC) for thermal unfolding analysis.
- Analytical ultracentrifugation and small-angle X-ray scattering (SAXS) for shape and oligomerization state determination.
Main Results:
- Purified human GrpE is folded, confirmed by CD measurements.
- Human GrpE exhibits distinct thermal unfolding characteristics compared to prokaryotic GrpE.
- Analytical ultracentrifugation and SAXS indicate human GrpE exists as an elongated dimer in solution.
- The low-resolution structure suggests a symmetric dimer for free human GrpE, contrasting with the asymmetric dimer of E. coli GrpE bound to DnaK.
Conclusions:
- Human mitochondrial GrpE forms a symmetric dimer in its free state.
- This symmetry contrasts with the asymmetric conformation of prokaryotic GrpE when bound to DnaK.
- The findings provide insights into GrpE's conformational flexibility and its mechanism of action in protein folding.