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Clathrin-coated vesicles from brain have small payloads: a cryo-electron tomographic study
J Bernard Heymann1, Dennis C Winkler, Yang-In Yim
1Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD 20892, United States.
Journal of Structural Biology
|May 22, 2013
Summary
Clathrin coats form complex structures during endocytosis. Most observed clathrin particles were empty baskets, with few containing actual vesicles, suggesting significant energy is used for membrane curvature stabilization.
Area of Science:
- Cell Biology
- Structural Biology
- Biophysics
Background:
- Clathrin coats are essential for endocytosis and intracellular trafficking, stabilizing membrane curvature.
- These coats assemble into polymorphic fullerene lattices with diverse geometries.
Purpose of the Study:
- To visualize and model the structures of clathrin-coated particles using cryo-electron tomography.
- To analyze the composition and geometry of clathrin-coated vesicles (CVs) and clathrin baskets.
Main Methods:
- Cryo-electron tomography was employed to image clathrin-coated particles from bovine brain.
- Polyhedral models were constructed for 54 distinct clathrin coat geometries.
Main Results:
- Observed particles ranged from 66-134nm; 80% were empty clathrin baskets, likely artifacts.
- True CVs (20%) showed vesicles offset within the coat, creating space for adaptor proteins.
- Cargo proteins were sparsely associated with the vesicle interior; clathrin, adaptors, and membrane constituted most CV mass.
Conclusions:
- Clathrin coat assembly is a significant biosynthetic investment relative to cargo size.
- This substantial effort may be necessary to overcome membrane resistance during high-curvature budding events.
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