BMAT: Self-assembly of extensin glycoproteins for designing novel plant-based biopolymers

地球上所有的生物都是由细胞组成的。每个细胞都被一个细胞外基质包围着。你可以把细胞外基质想象成一个保护和容纳细胞内容物的外壳。在植物中，这种外壳特别坚固和坚硬，由各种各样的生物聚合物组成。一种这样的聚合物被称为伸展蛋白。顾名思义，伸展蛋白在控制植物生长和伸展中起着重要作用，它通过形成聚合物分子支架或框架来实现这一目的。这项工作旨在了解是什么在分子水平上控制着支架的形成，以及我们如何利用这些知识来设计新的生物聚合物，模仿或模仿天然延伸蛋白的特性。面对全球气候变化，我们必须减少对化石燃料的依赖，不仅作为运输燃料，而且作为化学/聚合物原料。这项研究的潜在工业应用是众多的，包括生物降解塑料，分子电子学，食品增强，化妆品添加剂等的创造，这项研究也将提供培训机会forbudget和研究生在生物物理化学和生物化学。将开发新的物理化学和生物化学本科课程教材，并计划为小学/中学学龄儿童和成人开展各种推广和科学素养项目。技术摘要延伸蛋白（EXTs）是天然存在于植物细胞壁中的富含羟脯氨酸的糖蛋白。单体EXTs自组装形成不溶性聚合物细胞壁支架。很少有人知道是什么在分子水平上控制EXT自组装。原子力显微镜（AFM）以前已被用于探索EXT自组装的行为。这些研究表明EXT单体自发地自组装成复杂的树突状支架。此外，不同的EXT类型显示出不同的自组装行为，其中一些EXT更倾向于xy平面生长（称为“分支”），而另一些则显示z平面生长（称为“堆叠”）。这些变化归因于不同EXT所表现出的重复性、模块化和两亲性的差异。为了更好地理解EXT自组装的分子驱动因素，提出了三个目标。首先，将进一步表征天然EXT糖蛋白的自组装通过AFM研究其动力学，孔径，和相对增长的x-，y-和z-平面。然后，合成生物学将用于创建具有两亲性、模块化和重复性的仿生EXT，并使用原子力显微镜测试其自组装行为。最后，合成自组装EXT的生化和生物物理特性将被表征和比较，重点关注单体粘附强度和聚合物柔性。阐明控制EXT自组装的分子规则有望促进合成的、基于植物的仿生生物聚合物的合理设计。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical summaryAll living creatures on earth are made of cells. Each cell is enclosed by an extracellularmatrix. You can think of an extracellular matrix as a housing that protects and containsa cell’s contents. In plants, that housing is particularly strong and rigid and is composedof a wide variety of biopolymers. One such polymer is known as extensin. As its nameimplies, extensin plays an important role in controlling plant growth and extension, andit does so by forming a polymeric molecular scaffold or frame. This work aims tounderstand what governs scaffold formation at the molecular level and how we can usethis knowledge to design new biopolymers that mimic or imitate the properties ofnatural extensins. In the face of global climate change, our reliance on fossil fuels mustbe reduced, not only for use as transportation fuels, but also as chemical/polymerfeedstocks. Potential industrial applications of this research are numerous and includethe creation of biodegradable plastics, molecular electronics, food enhancement,cosmetics additives, etc. This research will also provide training opportunities forundergraduate and graduate students in biophysical chemistry and biochemistry. Newundergraduate course materials for physical chemistry and biochemistry will bedeveloped, and various outreach and scientific literacy projects for primary/secondaryschool aged children and adults are planned.Technical summaryExtensins (EXTs) are network-forming hydroxyproline-rich glycoproteins foundnaturally in plant cell walls. Monomeric EXTs self-assemble to form insoluble polymericcell wall scaffolds. Very little is known about what governs EXT self-assembly at themolecular level. Atomic force microscopy (AFM) has been previously used to explorethe behavior of EXT self-assembly. These studies showed that EXT monomersspontaneously self-assemble into intricate dendritic scaffolds. Furthermore, differentEXT types displayed different self-assembly behaviors, whereby some EXTs favoredmore xy-plane growth (termed ‘branching’), while others displayed z-plane growth(termed ‘stacking’). These changes were attributed to differences in the repetitive,modular, and amphiphilic nature exhibited by different EXTs. To better understand themolecular drivers of EXT self-assembly, three objectives are proposed. First, will befurther characterize the self-assembly of native EXT glycoproteins by AFM to studytheir kinetics, pore sizes, and relative growth in the x-, y-, and z-planes. Syntheticbiology will then be used to create biomimetic EXTs that vary in amphiphilicity,modularity, and repetitiveness and test for their self-assembly behavior using AFM.Lastly, the biochemical and biophysical properties of synthetic self-assembled EXTs willbe characterized and compared with a focus on monomer adhesion strength andpolymer flexibility. Elucidating the molecular rules that govern EXT self-assembly isexpected to facilitate the rational design of synthetic, plant-based biomimeticbiopolymers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.