Soft Matter Seminar: Clathrin triskelion flexibility, folding and self-assembly investigated by AFM

Friday, February 26, 2010 - 3:00pm - 4:15pm
Reiss 502
Svetlana Kotova

Direct visualization of protein conformations in physiological conditions is often challenging and yet more insightful than other measurements relying on population averaging. Atomic force microscopy (AFM), with both its imaging and force manipulation capability in aqueous environments, has become a potent research tool in biological investigations. In this study AFM imaging under physiologically relevant fluids and in air, along with single-molecule force spectroscopy (SMFS), was applied to characterize the structure and interaction properties of clathrin triskelia. The latter are basic building blocks of the protein coat surrounding plasma-membrane-derived vesicles (clathrin-coated vesicles) involved in receptor-mediated endocytosis. Defects in clathrin and related trafficking proteins correlate with a number of human diseases, including premature atherosclerosis, disorders in iron metabolism, and neurological problems. Our high-resolution AFM imaging under fluid and in air has provided new information about the macromolecular structure and assembly properties of clathrin triskelia. Direct AFM visualization demonstrated molecular flexibility within individual triskelia, as well as their dimerization and oligomerization in biological buffers. SMFS revealed a series of internal energetic barriers that characterize triskelion heavy chain unfolding. These results provide further understanding for molecular functionality of clathrin, and once again show AFM to be a powerful tool for biomedical imaging and nanometric single molecule characterizations.

Host: Daniel Blair