Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, 480 Ray C. Hunt Dr., Charlottesville, VA 22903, USA.
Science. 2020 Aug 28;369(6507):1089-1094. doi: 10.1126/science.abb2978. Epub 2020 Jul 9.
Cellulose is an essential plant cell wall component and represents the most abundant biopolymer on Earth. Supramolecular plant cellulose synthase complexes organize multiple linear glucose polymers into microfibrils as load-bearing wall components. We determined the structure of a poplar cellulose synthase CesA homotrimer that suggests a molecular basis for cellulose microfibril formation. This complex, stabilized by cytosolic plant-conserved regions and helical exchange within the transmembrane segments, forms three channels occupied by nascent cellulose polymers. Secretion steers the polymers toward a common exit point, which could facilitate protofibril formation. CesA's N-terminal domains assemble into a cytosolic stalk that interacts with a microtubule-tethering protein and may thus be involved in CesA localization. Our data suggest how cellulose synthase complexes assemble and provide the molecular basis for plant cell wall engineering.
纤维素是植物细胞壁的重要组成部分，也是地球上最丰富的生物聚合物。超分子植物纤维素合酶复合物将多个线性葡萄糖聚合物组织成微纤维作为承重的细胞壁成分。我们确定了杨树纤维素合酶 CesA 三聚体的结构，该结构为纤维素微纤维的形成提供了分子基础。这个复合物由细胞质中保守的区域稳定，并在跨膜区域内形成螺旋交换，形成三个由新生纤维素聚合物占据的通道。分泌将聚合物引导到共同的出口点，这可能有助于原纤维的形成。CesA 的 N 端结构域组装成一个细胞质茎，与微管结合蛋白相互作用，因此可能参与 CesA 的定位。我们的数据表明了纤维素合酶复合物是如何组装的，并为植物细胞壁工程提供了分子基础。
