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Probing the three-dimensional structure of human calreticulin
1School of Pharmacy, University of Connecticut, Storrs, Connecticut 06269, USA. bouvier@uconnvm.uconn.edu
Biochemistry
|December 2, 2000
Summary
Human calreticulin (CRT) is an elongated, flexible protein. Its structure, determined through biochemical and biophysical methods, suggests this flexibility is key to its molecular chaperone function in the endoplasmic reticulum.
Area of Science:
- Biochemistry
- Biophysics
- Structural Biology
Background:
- Calreticulin (CRT) is a key molecular chaperone in the endoplasmic reticulum lumen.
- CRT assists in the proper folding of nascent glycoproteins.
Purpose of the Study:
- To elucidate the three-dimensional structure of human CRT.
- To understand the molecular basis of CRT's chaperone activity.
Main Methods:
- Sedimentation analysis and chemical cross-linking to determine molecular mass and solution behavior.
- Hydrodynamic measurements (frictional ratio) to assess molecular shape.
- Far-UV circular dichroism for thermal stability analysis.
- Proteolysis experiments (thermolysin) to identify stable structural domains.
Main Results:
- Human CRT is monomeric with a molecular mass of approximately 46 kDa.
- Hydrodynamic data indicate an elongated, asymmetric molecular shape (29.8 nm length, 2.44 nm diameter).
- CRT exhibits marginal stability with a melting transition at 42.5°C.
- Proteolysis reveals a flexible C-terminal acidic segment and a stable core in the N- and P-domains.
Conclusions:
- Human CRT possesses an elongated and flexible structure in solution.
- This flexibility is likely crucial for its function as a molecular chaperone.
- The identified stable core and flexible regions provide insights into CRT's mechanism of action.