BMAT: Self-assembly of extensin glycoproteins for designing novel plant-based biopolymers

Ohio University, Athens OH

Investigators

Abstract

Non-technical summary All living creatures on earth are made of cells. Each cell is enclosed by an extracellular matrix. You can think of an extracellular matrix as a housing that protects and contains a cell’s contents. In plants, that housing is particularly strong and rigid and is composed of a wide variety of biopolymers. One such polymer is known as extensin. As its name implies, extensin plays an important role in controlling plant growth and extension, and it does so by forming a polymeric molecular scaffold or frame. This work aims to understand what governs scaffold formation at the molecular level and how we can use this knowledge to design new biopolymers that mimic or imitate the properties of natural extensins. In the face of global climate change, our reliance on fossil fuels must be reduced, not only for use as transportation fuels, but also as chemical/polymer feedstocks. Potential industrial applications of this research are numerous and include the creation of biodegradable plastics, molecular electronics, food enhancement, cosmetics additives, etc. This research will also provide training opportunities for undergraduate and graduate students in biophysical chemistry and biochemistry. New undergraduate course materials for physical chemistry and biochemistry will be developed, and various outreach and scientific literacy projects for primary/secondary school aged children and adults are planned. Technical summary Extensins (EXTs) are network-forming hydroxyproline-rich glycoproteins found naturally in plant cell walls. Monomeric EXTs self-assemble to form insoluble polymeric cell wall scaffolds. Very little is known about what governs EXT self-assembly at the molecular level. Atomic force microscopy (AFM) has been previously used to explore the behavior of EXT self-assembly. These studies showed that EXT monomers spontaneously self-assemble into intricate dendritic scaffolds. Furthermore, different EXT types displayed different self-assembly behaviors, whereby some EXTs favored more xy-plane growth (termed ‘branching’), while others displayed z-plane growth (termed ‘stacking’). These changes were attributed to differences in the repetitive, modular, and amphiphilic nature exhibited by different EXTs. To better understand the molecular drivers of EXT self-assembly, three objectives are proposed. First, will be further characterize the self-assembly of native EXT glycoproteins by AFM to study their kinetics, pore sizes, and relative growth in the x-, y-, and z-planes. Synthetic biology will then be used to create biomimetic EXTs that vary in amphiphilicity, modularity, and repetitiveness and test for their self-assembly behavior using AFM. Lastly, the biochemical and biophysical properties of synthetic self-assembled EXTs will be characterized and compared with a focus on monomer adhesion strength and polymer flexibility. Elucidating the molecular rules that govern EXT self-assembly is expected to facilitate the rational design of synthetic, plant-based biomimetic biopolymers. 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.