Crystal structures of an ATP-dependent hexokinase with broad substrate specificity from the hyperthermophilic archaeon Sulfolobus tokodaii
Crystal structures of an ATP-dependent hexokinase with broad substrate specificity from the hyperthermophilic archaeon Sulfolobus tokodaii
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DOI：
10.1074/jbc.m610678200
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发表时间：
2007-03-30
影响因子：
4.8
通讯作者：
Wakagi, Takayoshi
中科院分区：
文献类型：
--
作者：
Nishimasu, Hiroshi;Fushinobu, Shinya;Wakagi, Takayoshi
己糖激酶通过使用ATP作为磷酰基供体催化葡萄糖磷酸化为葡萄糖6-磷酸。最近，我们确定并表征了一个ATP依赖性己糖激酶（StHK）的超嗜热古菌硫化叶菌tokodaii，它可以磷酸化广泛的糖底物，包括葡萄糖，甘露糖，葡萄糖胺，和N-乙酰葡萄糖胺。在这里，我们提出了四种不同形式的StHK的晶体结构：（i）apo-形式，（ii）与葡萄糖的二元复合物，（iii）与ADP的二元复合物，和i与木糖，Mg 2+和ADP的四元复合物。形式i和iii处于开放状态，形式ii和iv处于闭合状态，表明糖结合诱导大的构象变化，而ADP结合不。同一种酶的四种不同的晶体结构提供了构象的“快照”。在催化循环中发生变化。StHK具有己糖激酶家族的核心折叠特征，但负责底物结合的几个环区的结构与其他已知己糖激酶家族成员的结构显著不同。StHK与人N-乙酰葡糖胺激酶和其他己糖激酶的结构比较为StHK磷酸化葡萄糖和N-乙酰葡糖胺的能力提供了解释。Mg 2+离子和配位水分子在四元络合物结构的电子密度中被很好地定义。这种结构代表了镁与己糖激酶结合模式的第一个直接可视化，因此可以更好地理解整个己糖激酶家族的催化机制。
Hexokinase catalyzes the phosphorylation of glucose to glucose 6-phosphate by using ATP as a phosphoryl donor. Recently, we identified and characterized an ATP-dependent hexokinase (StHK) from the hyperthermophilic archaeon Sulfolobus tokodaii, which can phosphorylate a broad range of sugar substrates, including glucose, mannose, glucosamine, and N-acetylglucosamine. Here we present the crystal structures of StHK in four different forms: (i) apo-form, (ii) binary complex with glucose, (iii) binary complex with ADP, and i quaternary complex with xylose, Mg2+, and ADP. Forms i and iii are in the open state, and forms ii and iv are in the closed state, indicating that sugar binding induces a large conformational change, whereas ADP binding does not. The four different crystal structures of the same enzyme provide "snapshots" of the conformational. changes during the catalytic cycle. StHK exhibits a core fold characteristic of the hexokinase family, but the structures of several loop regions responsible for substrate binding are significantly different from those of other known hexokinase family members. Structural comparison of StHK with human N-acetylglucosamine kinase and other hexokinases provides an explanation for the ability of StHK to phosphorylate both glucose and N-acetylglucosamine. A Mg2+ ion and coordinating water molecules are well defined in the electron density of the quaternary complex structure. This structure represents the first direct visualization of the binding mode for magnesium to hexokinase and thus allows for a better understanding of the catalytic mechanism proposed for the entire hexokinase family.