Subsequent projects | Special projects

Start of funding 01.07.2008

Single-Molecule Studies on the Dynamics of Chaperonin-Assisted Protein Folding using Microfludic Chambers

Prof. Don C. Lamb
Ludwig-Maximilians-University of Munich
Faculty for chemistry and pharmacy

Prof. Dr. Shimo Weiss
University of Southern California, Los Angeles
Department of Chemistry and Biochemistry


Chaperon proteins are present in all known organisms and assist a significant number of proteins in folding to their native structure within the cell cytosol. Proper folding of proteins is necessary for their functionality and protein misfolding is observed in different diseases such as Alzheimer or Parkinson. It was thought that chaperonins (a subclass of chaperon proteins) are not directly involved in the folding process but provide a protected environment where the nascent polypeptide chain can fold without deleterious interactions with other biomolecules in the cytosol. We have recently shown (Sharma et al, Cell 2008 133:142-153) that the chaperonin GroEL with its cofactor GroES is much more active in the folding process. The nascent ploy-peptide chain that binds to GroEL is transiently stretched and subsequently released into its cavity where folding occurs in a controlled manner. From our Single Molecule FRET measurement, we could distinguish different conformations of the substrate bound to GroEL. To investigate the kinetics of the individual subpopulations in chaperonin assisted protein folding, we will combine single molecule microscopy with microfluidic mixing.

Recently, the group of Prof. Shimon Weiss at the University of California, Los Angeles has used hydrodynamic focusing to produce rapid buffer exchange while simultaneously creating a thin stream of molecules suitable for single molecule detection (Hamadani and Weiss Biophys J 2008 10.1529/biophysj.107.127431). Combining this approach with our single molecule apparatus and Chaperonin system, we will be able to investigate the dynamics of single GroEL -substrate complexes upon addition of other compounds necessary for folding such as GroES or ATP. These experiments will provide a deeper insight into the pathway of chaperonin-assisted folding and how this complex protein folding machinery functions.