High-resolution crystal structures of the lectin-like xylan binding domain from Streptomyces lividans xylanase 10A with bound substrates reveal a novel mode of xylan binding
High-resolution crystal structures of the lectin-like xylan binding domain from Streptomyces lividans xylanase 10A with bound substrates reveal a novel mode of xylan binding
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DOI：
10.1021/bi015865j
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发表时间：
2002-04-02
期刊：
影响因子：
2.9
通讯作者：
Rose, DR
中科院分区：
文献类型：
--
作者：
Notenboom, V;Boraston, AB;Rose, DR
碳水化合物结合模块(CBM)家族13包括“R型”或“蓖麻毒素超家族”β-三叶凝集素。变铅青链霉菌木聚糖酶10A的C端CBM13是一个13型CBM家族，它不仅在结构上与R型凝集素相似，而且在功能上也有一些相似。CBM13的主要功能是结合木聚糖，但它保留了R型凝集素结合乳糖和半乳糖等小糖的能力。CBM13与木聚糖的结合似乎涉及CBM13的三个三叶结构域中的三个结合口袋的协同和相加参与，这表明了CBM-木聚糖相互作用的一种新机制。因此，CBM13与糖的相互作用显示出相当大的可塑性，我们为其提供了结构基础。CBM13的高分辨晶体结构是由CBM13与溴化配体形成的络合物的多重反常色散确定的。CBM13与乳糖和木戊糖形成的络合物具有两种不同的配体结合机制。CBM 13通过类似蓖麻毒素的结合在所有三个经典的三叶结合口袋中保留了其对乳糖的特异性。然而，CBM13具有结合乳糖的非还原半乳糖部分或还原葡萄糖部分的能力。木糖结合的模式提示三叶糖结合支架中的适应性突变，以适应木糖螺旋聚合物的内部结合。
Carbohydrate-binding module (CBM) family 13 includes the "R-type" or "ricin superfamily" beta-trefoil lectins. The C-terminal CBM, CBM13, of xylanase 10A from Streptomyces lividans is a family 13 CBM that is not only structurally similar to the "R-type" lectins but also somewhat functionally similar. The primary function of CBM13 is to bind the polysaccharide xylan, but it retains the ability of the R-type lectins to bind small sugars such as lactose and galactose. The association of CBM13 with xylan appears to involve cooperative and additive participation of three binding pockets in each of the three trefoil domains of CBM13, suggesting a novel mechanism of CBM-xylan interaction. Thus, the interaction of CBM13 with sugars displays considerable plasticity for which we provide a structural rationale. The high-resolution crystal structure of CBM13 was determined by multiple anomalous dispersion from a complex of CBM13 with a brominated ligand. Crystal structures of CBM 13 in complex with lactose and xylopentaose revealed two distinct mechanisms of ligand binding. CBM 13 has retained its specificity for lactose via Ricin-like binding in all of the three classic trefoil binding pockets. However, CBM13 has the ability to bind either the nonreducing galactosyl moiety or the reducing glucosyl moiety of lactose. The mode of xylopentaose binding suggests adaptive mutations in the trefoil sugar binding scaffold to accommodate internal binding on helical polymers of xylose.