Plant Protein Shape Puzzle Solved by Molecular 3-D Model

Researchers from North Carolina State University believe they have solved a puzzle that has vexed science since plants first appeared on Earth.

In a groundbreaking paper published online this week inProceedings of the National Academy of Sciences, the researchers provide the first three-dimensional model of an enzyme that links a simple sugar, glucose, into long-chain cellulose, the basic building block within plant cell walls that gives plants structure. Cellulose is nature’s most abundant renewable biomaterial and an important resource for production of biofuels that represent alternatives to fossil fuels.

例如，对模型植物酶，纤维素合成酶的结构的新了解，可以允许研究人员对更好的棉纤维或更强的木材的遗传工程工程和树木。从材料工程角度来看，发现也可用于产生具有所需性质和功能的有益纳米晶体。

“This structural model gives us insight into how cellulose synthesis works,” said Dr.Yaroslava yingling., an NC State materials science and engineering professor who is the corresponding author on the study. “In the long term, it could result in new genetically modified plants that can be tweaked to induce specific engineered properties of cellulose.”

The study examined the structure of one cellulose synthase found in cotton fibers. The researchers compared their model with the structure of a similar enzyme in bacteria and found that the proteins were similarly folded in key regions required for cellulose synthesis. In the lab rat of the plant family – Arabidopsis thaliana, or mustard weed – the researchers identified potential causes for defective cellulose synthesis in mutant plants by making analogies to the modeled cotton cellulose synthase.

“没有酶结构，你无法做出战略设计的，有理的理性预测如何对蛋白质进行有益的改变 - 但现在你可以，”博士说Candace Haigler, an NC State crop scientist and plant biologist who co-authored the study. “In the future we could make cellulose easier to break down into biofuels while ensuring that the plants themselves are able to grow well.”

Latsavongsakda Sethaphong, an NC State doctoral student, co-authored the study, as did researchers from Penn State University, the University of Virginia, the University of Ontario Institute of Technology and the University of Kentucky. The computational research was supported as part of The Center for LignoCellulose Structure and Formation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.

- kulikowski

Note to editors: An abstract of the paper follows.

Tertiary Model of a Plant Cellulose Synthase

Authors：Latsavongsakda Sethaphong，Candace H. Haigler和Yaroslava G. Yingling，北卡罗来纳州立大学;宾夕法尼亚州立大学詹姆斯D. Kubicki;弗吉尼亚大学Jochen Zimmer;安大略大学达里奥·博纳特理工学院;肯塔基州大学Seth Debolt

Published：2013年4月15日在线，在Proceedings of the National Academy of Sciences

Abstract：尽管超过四十多年的实验努力，但植物纤维素合酶（CESA）的三维原子模型仍然令人难以捉摸。在这里，我们在胞质区内报告了计算地预测了506个棉CESA氨基酸的三维结构。预测植物CESA结构与细菌纤维素合成蛋白质的溶解结构的比较验证了模拟的糖基转移酶（GT）结构域的整体折叠。共调配植物和细菌GT结构域共享六链β-片，五个β-β-β-片，以及类似于其他GT-2糖基转移酶的催化剂所需的基序。Extending beyond the cross-kingdom similarities related to cellulose polymerization, the predicted structure of cotton CESA reveals that plant specific modules (‘plant conserved region’, P-CR, and ‘class specific region’, CSR) fold into distinct subdomains on the periphery of the catalytic region. Computational results support the importance of the P-CR and/or CSR in CESA oligomerization to form the multimeric cellulose-synthesis complexes that are characteristic of plants. Relatively high sequence conservation between plant CESAs allowed mapping of known mutations and two novel mutations that perturb cellulose synthesis in Arabidopsis thaliana to their analogous positions in the modeled structure. Most of these mutations sites are near the predicted catalytic region, and the confluence of other mutation sites supports the existence of previously undefined functional nodes within the catalytic core of CESA. Overall, the predicted tertiary structure provides a platform for the biochemical engineering of plant CESAs.