Structural and biochemical characterization of a multidomain alginate lyase reveals a novel role of CBM32 in CAZymes
Structural and biochemical characterization of a multidomain alginate lyase reveals a novel role of CBM32 in CAZymes
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多域藻酸盐裂解酶的结构和生化特征揭示了 CBM32 在 CAZymes 中的新作用
DOI：
10.1016/j.bbagen.2018.05.024
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发表时间：
2018-09-01
影响因子：
3
通讯作者：
Liu, Weizhi
中科院分区：
文献类型：
--
作者：
Lyu, Qianqian;Zhang, Keke;Liu, Weizhi
非催化碳水化合物结合模块(CBM)已被证明与同源催化结构域起着不同的作用。然而，对于多糖裂解酶(Pls)，CBMS的作用大多尚不清楚。AIYB是一种含有CBM32和PL7催化结构域的多域海藻酸裂解酶。这里确定的Aiyb结构揭示了CBM32和催化域之间的非规范α螺旋连接物。更有趣的是，CBM32和连接物并没有显著提高催化活性，而是规定了降解产物中以三糖为主。详细的诱变、生化和共结晶分析表明，CBM32与海藻酸低聚糖的相互作用很弱，但很重要。结合分子模拟，我们认为CBM32结构域在三糖释放过程中是一个“支点”。总之，这项工作展示了CBMS在附加的PL结构域的活性中的新作用，并通过利用相关的CBMS为明确定义的藻酸盐低聚糖的产生提供了一条新的途径。
Noncatalytic carbohydrate binding modules (CBMs) have been demonstrated to play various roles with cognate catalytic domains. However, for polysaccharide lyases (PLs), the roles of CBMs remain mostly unknown. AIyB is a multidomain alginate lyase that contains CBM32 and a PL7 catalytic domain. The AIyB structure determined herein reveals a noncanonical alpha helix linker between CBM32 and the catalytic domain. More interestingly, CBM32 and the linker does not significantly enhance the catalytic activity but rather specifies that trisaccharides are predominant in the degradation products. Detailed mutagenesis, biochemical and cocrystallization analyses show "weak but important" CBM32 interactions with alginate oligosaccharides. In combination with molecular modeling, we propose that the CBM32 domain serves as a "pivot point" during the trisaccharide release process. Collectively, this work demonstrates a novel role of CBMs in the activity of the appended PL domain and provides a new avenue for the well-defined generation of alginate oligosaccharides by taking advantage of associated CBMs.