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Cellulose is one of the most abundant biopolymers for food, fiber and fuel. This versatile fiber is made by plant cellulose synthase, a plant membrane protein with a structural architecture that is not fully understood. PpCesA5 from an early moss plant Physcomitrium patens has been the protein of interest due to PpCesA5-specific homo-oligomerization. This oligomerization can form trimers and a hexamer of CesA trimers called cellulose synthase complexes (CSCs) found in moss plants. Our 2.8 Å PpCesA5 trimer cryo-EM structure revealed a novel tether pin region that tethers the intrinsically disordered N-terminal domain (NTD) of PpCesA5 to the protein main body. Such an interaction would hypothetically form NTD loops on a trimer, but intrinsically disordered regions are a challenge to observe in cryo-EM. A complementary technique called small-angle neutron scattering (SANS) showed the overall shape of PpCesA5 trimer with intrinsically disordered NTD loops. These loops could play a role in trimer-trimer oligomerization interactions in CSCs. This work presents the first cryo-EM structure of the Center for Nanophase Materials Sciences at ORNL in a joint collaboration with Penn State University. Overall, this research reveals new oligomerization mechanisms and informs rational design of biofuels and new biomaterials.

About the speaker:

Lynnicia Massenburg is currently a postdoc at the Center for Nanophase Materials Sciences (CNMS) at ORNL researching biotic and abiotic interfaces with cryo-electron microscopy (cryo-EM). This past Spring 2024, she earned her Ph.D. in Biochemistry, Microbiology and Molecular Biology from Pennsylvania State University. During her PhD, she was a 2022 SCGSR scholar in the Center for Structural Molecular Biology at ORNL focused on the cryo-EM structure of the plant membrane protein PpCesA5. She is a member of the Postdoctoral Sub-Committee in Microscopy Society for America and an At-Large Member for the CNMS User Experience Committee. She is also the founder of The Resilient Atom, a structure-based guide for mental resilience.

ORCID: Lynnicia Massenburg https://orcid.org/0000-0002-6590-273X