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A thermostable 35-residue subdomain within villin headpiece
C J McKnight1, D S Doering, P T Matsudaira
1Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge 02142, USA.
Journal of Molecular Biology
|July 12, 1996
Summary
The smallest protein domain, HP-35, from the actin-bundling protein villin, autonomously folds into a stable structure. This thermostable protein fragment demonstrates unique folding properties without needing disulfide bonds or ligand binding.
Area of Science:
- Protein structure and folding
- Biophysics
- Molecular biology
Background:
- Villin is an actin-bundling protein with a C-terminal f-actin binding domain called headpiece.
- The chicken villin headpiece is known for its high thermostability.
Purpose of the Study:
- To investigate the minimal structural unit responsible for the thermostability of the villin headpiece.
- To characterize the folding properties and structural integrity of this minimal domain.
Main Methods:
- Limited proteolysis to identify the stable subdomain.
- Circular dichroism and thermal denaturation assays to assess thermostability.
- Nuclear Magnetic Resonance (NMR) spectroscopy to study protein structure and dynamics.
Main Results:
- A 35-residue subdomain (HP-35) was identified as the core of the stable, folded structure.
- HP-35 is monomeric, highly thermostable (Tm ~70°C), and folds independently of ligands or metal ions.
- NMR data revealed three short alpha-helices within HP-35, consistent with the intact headpiece structure.
- HP-35 exhibits properties of a fully folded protein, not a molten globule.
Conclusions:
- The C-terminal 35 residues of villin headpiece (HP-35) constitute the smallest autonomously folding, thermostable protein domain composed of naturally occurring amino acids.
- HP-35 represents a unique model for studying protein folding, stability, and structure-function relationships.