Three-dimensional structure of the human transglutaminase 3 enzyme: binding of calcium ions changes structure for activation
Three-dimensional structure of the human transglutaminase 3 enzyme: binding of calcium ions changes structure for activation
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DOI：
10.1093/emboj/21.9.2055
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发表时间：
2002-05-01
期刊：
影响因子：
11.4
通讯作者：
Steinert, PM
中科院分区：
文献类型：
--
作者：
Ahvazi, B;Kim, HC;Steinert, PM
谷氨酰胺转酶（TGase）酶以钙依赖的方式催化蛋白质结合的谷氨酰胺和赖氨酸之间形成共价交联，但Ca2+离子的作用尚不清楚。TGase 3异构体广泛表达，对上皮屏障的形成很重要。它是一种酶原，需要蛋白水解才能产生活性。我们分别在2.2埃和2.1埃分辨率下解决了酶原和活化形式的三维结构，并研究了Ca2+离子的作用。酶原将一个不能交换的离子紧密地结合在一起。蛋白水解后，酶放热获得两个Ca2+离子，激活酶，是可交换的，并在功能上被其他镧系三价阳离子替代。Ca2+离子在其中一个位点的结合打开了一个通道，暴露了控制底物进入活性位点的关键Trp236和Trp327残基。总之，这些生化和结构数据首次揭示了Ca2+离子在TGase酶中诱导的结构变化，这些变化至少在一定程度上决定了活性，而且可能赋予底物特异性。
Transglutaminase (TGase) enzymes catalyze the formation of covalent cross-links between protein-bound glutamines and lysines in a calcium-dependent manner, but the role of Ca2+ ions remains unclear. The TGase 3 isoform is widely expressed and is important for epithelial barrier formation. It is a zymogen, requiring proteolysis for activity. We have solved the three-dimensional structures of the zymogen and the activated forms at 2.2 and 2.1 Angstrom resolution, respectively, and examined the role of Ca2+ ions. The zymogen binds one ion tightly that cannot be exchanged. Upon proteolysis, the enzyme exothermally acquires two more Ca2+ ions that activate the enzyme, are exchangeable and are functionally replaceable by other lanthanide trivalent cations. Binding of a Ca2+ ion at one of these sites opens a channel which exposes the key Trp236 and Trp327 residues that control substrate access to the active site. Together, these biochemical and structural data reveal for the first time in a TGase enzyme that Ca2+ ions induce structural changes which at least in part dictate activity and, moreover, may confer substrate specificity.