School of Fundamental Sciences, Massey University, PN461, Private Bag 11222, Palmerston North 4442, New Zealand.
MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand.
Biomacromolecules. 2020 Apr 13;21(4):1450-1459. doi: 10.1021/acs.biomac.9b01756. Epub 2020 Mar 4.
Evidence is presented that the polysaccharide rhamnogalacturonan I (RGI) can be biosynthesized in remarkably organized branched configurations and surprisingly long versions and can self-assemble into a plethora of structures. AFM imaging has been applied to study the outer mucilage obtained from wild-type (WT) and mutant ( and ) seeds. For WT mucilage, ordered, multichain structures of the polysaccharide RGI were observed, with a helical twist visible in favorable circumstances. Molecular dynamics (MD) simulations demonstrated the stability of several possible multichain complexes and the possibility of twisted fibril formation. For seeds, the imaged polymers clearly showed the presence of side chains. These were surprisingly regular and well organized with an average length of ∼100 nm and a spacing of ∼50 nm. The heights of the side chains imaged were suggestive of single polysaccharide chains, while the backbone was on average 4 times this height and showed regular height variations along its length consistent with models of multichain fibrils examined in MD. Finally, in mucilage extracts from seeds, a minor population of chains in excess of 30 μm long was observed.
有证据表明，多糖鼠李半乳糖醛酸聚糖 I（RGI）可以以非常有组织的分支结构和惊人的长链形式生物合成，并可以自组装成多种结构。原子力显微镜（AFM）成像已被应用于研究来自野生型（WT）和突变型（和）种子的外黏液。对于 WT 黏液，观察到多糖 RGI 的有序、多链结构，在有利条件下可见螺旋扭曲。分子动力学（MD）模拟表明，几种可能的多链复合物的稳定性以及扭曲纤维形成的可能性。对于种子，成像的聚合物清楚地显示了侧链的存在。这些侧链非常规则且组织有序，平均长度约为 100nm，间距约为 50nm。成像的侧链高度表明存在单多糖链，而主链的平均高度是其 4 倍，并且沿其长度显示出与 MD 中检查的多链纤维模型一致的规则高度变化。最后，在种子黏液提取物中，观察到长度超过 30μm的链的小部分。
