Crystal structure and mechanism of human L-arginine:glycine amidinotransferase: A mitochondrial enzyme involved in creatine biosynthesis
Crystal structure and mechanism of human L-arginine:glycine amidinotransferase: A mitochondrial enzyme involved in creatine biosynthesis
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DOI：
10.1093/emboj/16.12.3373
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发表时间：
1997-06-16
期刊：
影响因子：
11.4
通讯作者：
Huber, R
中科院分区：
文献类型：
--
作者：
Humm, A;Fritsche, E;Huber, R
L-精氨酸：甘氨酸脒基转移酶（AT）通过形成肌酸的直接前体胍基乙酸催化肌酸生物合成中的关键步骤。我们已经确定了重组人酶的晶体结构的多个同晶置换在1.9埃分辨率。在序列分配中使用碲甲硫氨酸衍生物。AT的结构揭示了一个新的折叠，具有圆形排列的β β α β-模块的5重假对称性。这些模块包围了活性部位室，只能通过狭窄的通道进入。整体结构类似于一个带有手柄的篮子，手柄由插入β β α β-模块形成。L-鸟氨酸（一种产物抑制剂）的结合揭示了一种明显的诱导配合机制，活性位点入口处的环改变了其构象，伴随着α-螺旋的位移，接近4埃。精氨酸离析物与失活突变体C407 A的结合显示出类似的结合模式。基于底物和产物的结合态，提出了一种具有催化三联体Cys-His-Asp的反应机理。
L-arginine:glycine amidinotransferase (AT) catalyses the committed step in creatine biosynthesis by formation of guanidinoacetic acid, the immediate precursor of creatine. We have determined the crystal structure of the recombinant human enzyme by multiple isomorphous replacement at 1.9 Angstrom resolution. A telluromethionine derivative was used in sequence assignment. The structure of AT reveals a new fold with 5-fold pseudosymmetry of circularly arranged beta beta alpha beta-modules These enclose the active site compartment, which is accessible only through a narrow channel. The overall structure resembles a basket with handles that are formed from insertions into the beta beta alpha beta-modules Binding of L-ornithine, a product inhibitor, reveals a marked induced-fit mechanism, with a loop at the active site entrance changing its conformation accompanied by a shift of an alpha-helix by similar to 4 Angstrom. Binding of the arginine educt to the inactive mutant C407A shows a similar mode of binding. A reaction mechanism with a catalytic triad Cys-His-Asp is proposed on the basis of substrate and product bound states.