Crystal structures of the sugar complexes of Streptomyces olivaceoviridis E-86 xylanase:: Sugar binding structure of the family 13 carbohydrate binding module
Crystal structures of the sugar complexes of Streptomyces olivaceoviridis E-86 xylanase:: Sugar binding structure of the family 13 carbohydrate binding module
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DOI：
10.1006/jmbi.2001.5338
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发表时间：
2002-02-08
影响因子：
5.6
通讯作者：
Mizuno, H
中科院分区：
文献类型：
--
作者：
Fujimoto, Z;Kuno, A;Mizuno, H
来自橄榄绿链霉菌E-86的家族10木聚糖酶含有作为催化结构域的（β/α）（8）-桶、作为木聚糖结合结构域（XBD）的家族13碳水化合物结合模块（CBM）以及它们之间的富含Gly/Pro的接头。这种酶的晶体结构表明，XBD具有三个类似的亚结构域，如三重重复序列的存在所示，形成类似于蓖麻毒素B链中发现的半乳糖结合凝集素折叠。与蓖麻毒素/乳糖复合物的结构的比较表明，在XBD的三个潜在的糖结合位点。为了了解XBD如何与木聚糖链结合，我们使用低聚木糖和其他糖通过浸泡实验方法分析了糖复合物的结构。在催化裂缝中，在木二糖和木三糖复合物结构中观察到结合糖。在XBD中，在与木糖、木二糖、木三糖、葡萄糖、半乳糖和乳糖的所有复合物中的亚结构域7和γ中鉴定了结合糖。XBD在与蓖麻毒素/乳糖复合物相同的糖结合位点结合木糖或低聚木糖，但其对木糖和低聚木糖的结合方式与蓖麻毒素中的半乳糖结合模式不同，即使XBD以与蓖麻毒素/半乳糖复合物相同的方式结合半乳糖。这些不同的结合模式被有效地和不同地用于将长底物与木聚糖酶和蓖麻毒素型凝集素结合。XBD可以结合木聚糖骨架中的任何木糖，而蓖麻毒素型凝集素识别末端半乳糖以夹持大的糖链，即使这两个结构域具有相同的家族13 CBM结构。家族13 CBM具有相当松散和广泛的糖特异性，并且被某些类型的蛋白质用于结合其靶糖。在这样的酶中，XBD结合木聚糖，并且催化结构域可以相对于XBD/木聚糖复合物呈现柔性位置，因为接头区是非结构化的。(C)2002年爱思唯尔科学有限公司
The family 10 xylanase from Streptomyces olivaceoviridis E-86 contains a (beta/alpha)(8)-barrel as a catalytic domain, a family 13 carbohydrate binding module (CBM) as a xylan binding domain (XBD) and a Gly/Pro-rich linker between them. The crystal structure of this enzyme showed that XBD has three similar subdomains, as indicated by the presence of a triple-repeated sequence, forming a galactose binding lectin fold similar to that found in the ricin toxin B-chain. Comparison with the structure of ricin/lactose complex suggests three potential sugar binding sites in XBD. In order to understand how XBD binds to the xylan chain, we analyzed the sugar-complex structure by the soaking experiment method using the xylooligosaccharides and other sugars. In the catalytic cleft, bound sugars were observed in the xylobiose and xylotriose complex structures. In the XBD, bound sugars were identified in subdomains 7 and gamma in all of the complexes with xylose, xylobiose, xylotriose, glucose, galactose and lactose. XBD binds xylose or xylooligosaccharides at the same sugar binding sites as in the case of the ricin/lactose complex but its binding manner for xylose and xylooligosaccharides is different from the galactose binding mode in ricin, even though XBD binds galactose in the same manner as in the ricin/galactose complex. These different binding modes are utilized efficiently and differently to bind the long substrate to xylanase and ricin-type lectin. XBD can bind any xylose in the xylan backbone, whereas ricin-type lectin recognizes the terminal galactose to sandwich the large sugar chain, even though the two domains have the same family 13 CBM structure. Family 13 CBM has rather loose and broad sugar specificities and is used by some kinds of proteins to bind their target sugars. In such enzyme, XBD binds xylan, and the catalytic domain may assume a flexible position with respect to the XBD/xylan complex, inasmuch as the linker region is unstructured., (C) 2002 Elsevier Science Ltd.