3D structural analysis of protein O-mannosyl kinase, POMK, a causative gene product of dystroglycanopathy
3D structural analysis of protein O-mannosyl kinase, POMK, a causative gene product of dystroglycanopathy
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DOI：
10.1111/gtc.12480
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发表时间：
2017-04-01
期刊：
影响因子：
2.1
通讯作者：
Yamaguchi, Yoshiki
中科院分区：
文献类型：
--
作者：
Nagae, Masamichi;Mishra, Sushil K.;Yamaguchi, Yoshiki
参与o -甘露糖聚糖合成的多种酶的协同作用提供了-三聚糖聚糖（-DG）上的基质聚糖，它吸引细胞外基质（ECM）蛋白质，如层粘连蛋白。异常的-DG的o -甘露糖基化导致严重的先天性肌营养不良，这是由于ECM蛋白从基底膜上脱离所致。蛋白o -甘露糖基激酶（POMK）催化的o -甘露糖c6位点磷酸化是o -甘露糖聚糖生物合成途径中的关键步骤。已知POMK催化结构域的几种错义突变可导致严重的先天性肌营养不良，即沃克-沃伯格综合征。由于与其他典型激酶的序列相似性较低，该酶的结构-活性关系尚不清楚。在这里，我们报道了在ATP类似物和o -甘露糖基化糖肽存在和不存在的情况下POMK催化结构域的晶体结构。POMK催化结构域为典型的蛋白激酶折叠，由N-叶和c -叶组成。甘露糖残基主要通过c2位置的羟基与POMK结合，区别于其他单糖残基。有趣的是，与ATP三磷酸基团相互作用的两个氨基酸残基K92和D228来自初级结构的非典型位置。这种蛋白质的突变导致肌肉萎缩症现在可以解释了。
Orchestration of the multiple enzymes engaged in O-mannose glycan synthesis provides a matriglycan on -dystroglycan (-DG) which attracts extracellular matrix (ECM) proteins such as laminin. Aberrant O-mannosylation of -DG leads to severe congenital muscular dystrophies due to detachment of ECM proteins from the basal membrane. Phosphorylation at C6-position of O-mannose catalyzed by protein O-mannosyl kinase (POMK) is a crucial step in the biosynthetic pathway of O-mannose glycan. Several mis-sense mutations of the POMK catalytic domain are known to cause a severe congenital muscular dystrophy, Walker-Warburg syndrome. Due to the low sequence similarity with other typical kinases, structure-activity relationships of this enzyme remain unclear. Here, we report the crystal structures of the POMK catalytic domain in the absence and presence of an ATP analogue and O-mannosylated glycopeptide. The POMK catalytic domain shows a typical protein kinase fold consisting of N- and C-lobes. Mannose residue binds to POMK mainly via the hydroxyl group at C2-position, differentiating from other monosaccharide residues. Intriguingly, the two amino acid residues K92 and D228, interacting with the triphosphate group of ATP, are donated from atypical positions in the primary structure. Mutations in this protein causing muscular dystrophies can now be rationalized.