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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Cellulosome assembly revealed by the crystal structure of the cohesin-dockerin complex
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Cellulosome assembly revealed by the crystal structure of the cohesin-dockerin complex

机译：粘着蛋白-dockerin复合物的晶体结构揭示了纤维素的组装

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摘要

The utilization of organized supramolecular assemblies to exploit the synergistic interactions afforded by close proximity, both for enzymatic synthesis and for the degradation of recalcitrant substrates, is an emerging theme in cellular biology. Anaerobic bacteria harness a multiprotein complex, termed the "cellulosome," for efficient degradation of the plant cell wall. This megadalton catalytic machine organizes an enzymatic consortium on a multi-faceted molecular scaffold whose "cohesin" domains interact with corresponding "dockerin" domains of the enzymes. Here we report the structure of the cohesin-dockerin complex from Clostridium thermocellum at 2.2-A resolution. The data show that the β-sheet cohesin domain interacts predominantly with one of the helices of the dockerin. Whereas the structure of the cohesin remains essentially unchanged, the loop-helix-helix-loop-helix motif of the dockerin undergoes conformational change and ordering compared with its solution structure, although the classical 12-residue EF-hand coordination to two calcium ions is maintained. Significantly, internal sequence duplication within the dockerin is manifested in near-perfect internal twofold symmetry, suggesting that both "halves" of the dockerin may interact with cohesins in a similar manner, thus providing a higher level of structure to the cellulosome and possibly explaining the presence of "polycellulo-somes." The structure provides an explanation for the lack of cross-species recognition between cohesin-dockerin pairs and thus provides a blueprint for the rational design, construction, and exploitation of these catalytic assemblies.
机译：利用有组织的超分子组装物来利用紧密接近提供的协同相互作用，无论是酶促合成还是难降解底物的降解，都是细胞生物学中的新兴主题。厌氧细菌利用一种称为“纤维素体”的多蛋白复合物来有效降解植物细胞壁。这种百万达尔顿催化机器在多面分子支架上组织了一个酶联体，该分子支架的“ cohesin”结构域与酶的相应“ dockerin”结构域相互作用。在这里，我们以2.2-A的分辨率报告了热纤梭菌黏附素-dockerin复合物的结构。数据显示，β-sheet黏附素结构域主要与dockerin的螺旋之一相互作用。尽管凝聚素的结构基本保持不变，但与之相比，dockerin的loop-helix-helix-loop-helix基序与其溶液结构相比发生构象变化和有序排列，尽管经典的十二残基EF-手与两个钙离子的配位是保持。重要的是，dockerin内部的内部序列重复表现为近乎完美的内部双重对称性，这表明dockerin的“两半”可能以相似的方式与cohesins相互作用，从而为纤维素体提供了更高水平的结构，并可能解释了存在“多纤维体”。该结构提供了对粘着蛋白-泊坞蛋白对之间缺乏跨物种识别的解释，从而为这些催化组件的合理设计，构建和开发提供了蓝图。

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