Structure determination of moss PpCesA5 cellulose synthase trimer*

Plant membrane proteins called cellulose synthases (CesAs) make cellulose, the most abundant plant polymer in the world found in plant cell walls. The cryo-EM structure of poplar PttCesA8 trimer has revealed structural insights, but an evolutionary context of CesA structure in other plant species is needed. The aim of my research proposal is to understand the role of plant CesA trimer oligomerization in functional cellulose synthesis and assembly. To approach this aim, I seek to characterize the structure of an early plant moss PpCesA5 in detergent and nanodiscs using SAXS/SANS and cryo-Electron Microscopy (cryo-EM). This structural analysis will provide information on residue-level oligomer interactions and global conformation of moss PpCesA5 trimers. Thus far, PpCesA5 has been successfully expressed in Sf9 cells. Current work involves optimizing the purification of higher order PpCesA5 oligomerization to capture this protein as a trimer and a hexamer of trimers. Future work involves an evolutionary structure comparison with poplar PttCesA8 and cotton GhCesA7 for insights on domains involved in oligomerization and function. This work reveals the importance of structural techniques such as cryo-EM to advance future work in biofuels and new biomaterials.