Cellulose synthesis in plants is carried out by the synergistic action of a large number of membrane bound cellulose synthase (CESA) proteins that form the cellulose synthesis complex (CSC). Knowledge of the structure of individual CESA proteins that form the CSC would provide critical information about the molecular mechanism of cellulose synthesis. Plant CESA proteins are single polypeptide chains of approximately 1000 amino acids. They have three major domains; an N-terminal domain that contains a Zn ring motif, a cytosolic catalytic domain, and a transmembrane domain. Here, we report on our progress in investigating the structures of individual domains of CESA proteins using small-angle scattering (SAS) and transmission electron microscopy (TEM) techniques complemented by computational methods, to gain insight into their role in the assembly and stabilization of the CSC. Ab initio models for the catalytic domain of Arabidopsis CESA1 (CESAcatD) derived from the small-angle neutron and X-ray scattering provide the first experimental evidence to support the self-assembly of CESAcatD monomers into stable homotrimer complexes [1]. Possible configurations for the arrangement of CESAcatD monomers in the homotrimer were obtained using computational modeling in which the class specific region is found at the periphery of the complex and the plant-conserved region forms the base of the trimer. The results of this study and TEM analysis of Physcomitrella patens CSC supported by computation, provide strong evidence that there are 18 CESA proteins in the plant CSC [1,2]. SAS, TEM, and computational analysis of the N-terminal domains of Arabidopsis and cotton CESA show that the proteins form stable dimers and provide new insights into the dimerization interface. The experimental and computational results will be discussed in the context of previously published work that proposed a redox dependent N-terminal domain dimerization mechanism and more recent work on in vitro synthesis of cellulose by heterologously expressed CESA proteins [3,4].

Organization of domains in CESA proteins of the plant cellulose synthesis complex

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.