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首页> 外文期刊>Nature structural biology >STRUCTURE AND MECHANISM OF ENDO/EXOCELLULASE E4 FROM THERMOMONOSPORA FUSCA
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STRUCTURE AND MECHANISM OF ENDO/EXOCELLULASE E4 FROM THERMOMONOSPORA FUSCA

机译:褐热菌内膜/外切酶E4的结构与机制

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摘要

Cellulase E4 from Thermomonospora fusca is unusual in that it has characteristics of both exo- and endo-cellulases. Here we report the crystal structure of a 68K M-r fragment of E4 (E4-68) at 1.9 Angstrom resolution. E4-68 contains both a family 9 catalytic domain, exhibiting an (alpha/alpha)(6) barrel fold, and a family III cellulose binding domain, having an antiparallel beta-sandwich fold. While neither of these folds is novel, E4-68 provides the first cellulase structure having interacting catalytic and cellulose binding domains. The complexes of E4-68 with cellopentaose, cellotriose and cellobiose reveal conformational changes associated with ligand binding and allow us to propose a catalytic mechanism for family 9 enzymes. We also provide evidence that E4 has two novel characteristics: first it combines exo- and endo-activities and second, when it functions as an exo-cellulase, it cleaves off cellotetraose units. [References: 59]
机译:来自热单孢菌的纤维素酶E4是不寻常的,因为它具有外切和内切纤维素酶的特征。在这里,我们报告了E4(E4-68)的68K M-r片段在1.9埃分辨率下的晶体结构。 E4-68既包含展现出(alpha / alpha)(6)桶形折叠的家族9催化结构域,又具有具有反平行的β-三明治折叠结构的III类纤维素结合域。尽管这些折叠都不是新颖的,但是E4-68提供了具有相互作用的催化和纤维素结合结构域的第一纤维素酶结构。 E4-68与纤维戊糖,纤维三糖和纤维二糖的复合物揭示了与配体结合相关的构象变化,并允许我们提出家族9酶的催化机制。我们还提供证据,证明E4具有两个新颖的特征:首先,它结合了外切和内切活性;其次,当它作为外切纤维素酶起作用时,它会切割掉纤维四糖单元。 [参考:59]

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