Obtaining 3D structures with subnanogram macromolecules

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DESCRIPTION (provided by applicant): Structural studies of biological macromolecules always start with producing the molecules in microgram to milligram quantities suitable for single molecule electron microscopy (EM), X-ray crystallography or NMR measurement. With subnanogram amount of biological macromolecules, it is prohibitively difficult to obtain their three-dimensional (3D) structures using the current technology. We propose to develop innovative technology that will overcome the quantity limit and obtain 3D structures from subnanogram quantities of biological complexes using single molecule EM. The key innovation will be to develop affinity-based methods that will specifically enrich low-abundance biological macromolecules onto carbon films and prepare them for single molecule EM and 3D reconstruction. The feasibility of this technology will be examined by introducing specific biological ligands to the surface of thin carbon films and evaluating the selective binding of cognate biological complexes, and by applying a Ni-chelating surface to the enrichment of a His-tagged protein complex (KvAP/Fv) for calculating its 3D structure. To test the application to a low- abundance complex, we will enrich functional human telomerase complex to the surface of modified carbon films and generate its first 3D structure. In summary, successful advancement of the new technology will make it possible to generate structures of many multi-component complexes only available at subnanogram levels.