CAREER:Understanding ferritin biomineralization by high-resolution cryo-electron microscopy

Arizona State University, Scottsdale AZ

Investigators

Abstract

NON-TECHNICAL SUMMARY Biological molecules are capable of interacting with inorganic materials, giving rise to highly controlled material synthesis and the creation of new bio-inorganic materials with unique function and properties. However, little is known about the molecular interactions between the biological molecules with inorganic materials. One of the most well studied proteins that controls the growth of inorganic materials is ferritin, which is a natural biomineralizing protein and is responsible for controlling the growth of iron oxide nanoparticles and maintaining proper levels of free iron in the cell. The focus of this CAREER project is to extend the powerful methods of single-particle cryo-electron microscopy (cryo-EM) along with high-resolution transmission electron microscopy methods (HRTEM) used in materials science to ferritin macromolecules in the process of nanomaterial growth. This project will ultimately make significant contributions to both the understanding of how the important ferritin protein functions and the general molecular interactions of biomolecules with nanomaterials. The next major advances in the field of biomolecule driven nanomaterial synthesis will be the ability to rationally design biomolecules for novel, highly controlled nanostructure synthesis. One of the biggest roadblocks to achieving these goals is the lack of understanding of how these biological molecules interface with the inorganic nanomaterials. The new cryo-EM methods developed in this proposal and the new knowledge gained about ferritin mediated nanoparticle synthesis will be able to be extended to many other biological-nanomaterial systems. Additionally, the project will initiate an interdisciplinary education program that educates the public and trains the next generation of scientists and engineers at the intersection between biology and materials science. TECHNICAL SUMMARY Despite the fact that ferritin is one of the most well-studied protein-nanoparticle systems, the fundamental interactions between ferritin and iron oxide nanoparticles grown inside its hollow core are not well-understood. The research in this CAREER proposal will produce new knowledge by determining the high-resolution structures of ferritins in the process of inorganic nanomaterial formation, from initial iron oxide nucleation to formed nanoparticles. The goal of correlating ferritin structure with the process of nanoparticle growth and ultimate material structure will be accomplished through the following technical objectives: (1) Elucidate the process of ferritin-controlled nanoparticle growth by high-resolution time-resolved single particle cryo-EM; (2) Determine the molecular interactions at the protein-nanoparticle interface by combined protein and nanomaterial structure determination. The project will make novel use of cryo-electron microscopy along with high-resolution transmission electron microscopy (HRTEM), and the combined use of both of these techniques on biomineralizing ferritin will require the development, optimization, and implementation of new methods for both techniques. The project aims to answer fundamental mechanisms of ferritin-controlled nanoparticle growth at the bio-inorganic interface, and the influences this interface has on the resulting iron oxide nanoparticle structure. Not only will this answer questions related to how ferritin interacts with inorganic materials, but this project would provide new understandings of the general interactions biological materials have with inorganic particles and surfaces. This would represent the first time many of these interactions have been directly visualized at this level of detail, both in terms of time resolution and spatial resolution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.