Crystal structure of baculovirus RNA triphosphatase complexed with phosphate
Crystal structure of baculovirus RNA triphosphatase complexed with phosphate
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DOI：
10.1074/jbc.m500885200
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发表时间：
2005-05-06
影响因子：
4.8
通讯作者：
Mondragón, A
中科院分区：
文献类型：
--
作者：
Changela, A;Martins, A;Mondragón, A
杆状病毒RNA 5'-三磷酸酶（BVP）是一类RNA特异性半胱氨酸磷酸酶，包括后生动物和植物mRNA盖顶酶的RNA三磷酸酶结构域。在这里，我们报道了在1.5埃分辨率的磷酸盐结合状态下BVP的晶体结构。BVP采用半胱氨酸磷酸酶α / β折叠的特征，并在活性位点区域结合两个磷酸离子，其中一个离子被提议模拟共价磷酸酶中间体水解后产物复合物的磷酸。晶体结构突出了主链酰胺和p环基序侧链（118）HCTHGXNRT（126）在结合可切割磷酸盐和稳定过渡态中的作用。将BVP结构与哺乳动物RNA三磷酸酶的脱酶进行比较，发现Arg-125侧链（直接与磷酸结合）的协同运动和活性位点上磷酸的相关表面环的关闭。该结构突出了Asn-124的直接催化作用，Asn-124是RNA三磷酸酶家族的标志性p环残基，可能是BVP水解磷酸酸酐键特异性的决定因素。
Baculovirus RNA 5'-triphosphatase (BVP) exemplifies a family of RNA-specific cysteine phosphatases that includes the RNA triphosphatase domains of metazoan and plant mRNA capping enzymes. Here we report the crystal structure of BVP in a phosphate-bound state at 1.5 angstrom resolution. BVP adopts the characteristic cysteine-phosphatase alpha/beta fold and binds two phosphate ions in the active site region, one of which is proposed to mimic the phosphate of the product complex after hydrolysis of the covalent phosphoenzyme intermediate. The crystal structure highlights the role of backbone amides and side chains of the P-loop motif (118)HCTHGXNRT(126) in binding the cleavable phosphate and stabilizing the transition state. Comparison of the BVP structure to the apoenzyme of mammalian RNA triphosphatase reveals a concerted movement of the Arg-125 side chain ( to engage the phosphate directly) and closure of an associated surface loop over the phosphate in the active site. The structure highlights a direct catalytic role of Asn-124, which is the signature P-loop residue of the RNA triphosphatase family and a likely determinant of the specificity of BVP for hydrolysis of phosphoanhydride linkages.