Crystal Structures of Putative Sugar Kinases from Synechococcus Elongatus PCC 7942 and Arabidopsis Thaliana.
Crystal Structures of Putative Sugar Kinases from Synechococcus Elongatus PCC 7942 and Arabidopsis Thaliana.
复制标题
细长聚球藻 PCC 7942 和拟南芥的假定糖激酶的晶体结构
DOI：
10.1371/journal.pone.0156067
复制
发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Chang W
中科院分区：
文献类型：
--
作者：
Xie Y;Li M;Chang W
细长聚球藻菌株PCC 7942的基因组编码推定的糖激酶（SePSK），其与来自拟南芥的木酮糖激酶-1（AtXK-1）具有44.9%的序列同一性。序列比对表明，这两种激酶属于核蛋白激酶样碳水化合物激酶，FGGY家族碳水化合物激酶的一个亚家族。然而，它们的确切生理功能和真实的底物仍然未知。在这里，我们解决了SePSK和AtXK-1的结构在其载脂蛋白形式和与核苷酸底物的复合物。这两种激酶表现出几乎相同的整体结构，在没有底物的情况下，两种激酶都具有ATP水解活性。此外，我们的酶促实验表明，SePSK具有磷酸化D-核酮糖的能力。为了研究SePSK的催化机理，我们解析了SePSK与D-核酮糖复合物的结构，发现SePSK中存在两个潜在的底物结合口袋。通过突变和活性分析，我们进一步验证了其催化活性的重要关键残基。此外，我们与其他家庭成员的结构比较表明，有主要的构象变化，在SePSK底物结合后，促进催化过程。总之，这些结果提供了重要的信息，更详细地了解辅因子和底物结合模式，以及SePSK的催化机制，并可能与其植物同系物AtXK-1的相似之处。
The genome of the Synechococcus elongatus strain PCC 7942 encodes a putative sugar kinase (SePSK), which shares 44.9% sequence identity with the xylulose kinase-1 (AtXK-1) from Arabidopsis thaliana. Sequence alignment suggests that both kinases belong to the ribulokinase-like carbohydrate kinases, a sub-family of FGGY family carbohydrate kinases. However, their exact physiological function and real substrates remain unknown. Here we solved the structures of SePSK and AtXK-1 in both their apo forms and in complex with nucleotide substrates. The two kinases exhibit nearly identical overall architecture, with both kinases possessing ATP hydrolysis activity in the absence of substrates. In addition, our enzymatic assays suggested that SePSK has the capability to phosphorylate D-ribulose. In order to understand the catalytic mechanism of SePSK, we solved the structure of SePSK in complex with D-ribulose and found two potential substrate binding pockets in SePSK. Using mutation and activity analysis, we further verified the key residues important for its catalytic activity. Moreover, our structural comparison with other family members suggests that there are major conformational changes in SePSK upon substrate binding, facilitating the catalytic process. Together, these results provide important information for a more detailed understanding of the cofactor and substrate binding mode as well as the catalytic mechanism of SePSK, and possible similarities with its plant homologue AtXK-1.