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Protein interactions and misfolding analyzed by AFM force spectroscopy
Chad McAllister1, Mikhail A Karymov, Yoshiko Kawano
1School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
Journal of Molecular Biology
|November 18, 2005
Summary
Protein misfolding, a key step in aggregate formation, is driven by pH-dependent structural changes. Lowering pH induces conformational transitions, increasing intermolecular forces and promoting amyloid fibril assembly.
Area of Science:
- Biochemistry
- Biophysics
- Structural Biology
Background:
- Protein misfolding and aggregation are implicated in various diseases.
- While protein aggregation is common, the precise mechanisms increasing intermolecular interactions during misfolding remain unclear.
Purpose of the Study:
- To investigate the relationship between protein conformational changes and intermolecular forces at varying pH.
- To elucidate how pH influences protein self-assembly into aggregates.
Main Methods:
- Atomic Force Microscopy (AFM) to measure interprotein forces.
- Circular Dichroism (CD) spectroscopy to analyze protein secondary structure.
- AFM imaging to study protein aggregate formation.
Main Results:
- Attractive forces between protein molecules significantly increase at acidic pH.
- Acidic pH induces a conformational transition from random coil to beta-sheet structures.
- Protein aggregation into filamentous structures is enhanced at low pH, correlating with increased interprotein forces.
Conclusions:
- pH-induced conformational transitions in proteins enhance interprotein interactions.
- These transitions are a primary driver for protein self-assembly and aggregate formation.
- The findings provide direct evidence linking protein structure, intermolecular forces, and aggregation propensity.