Determinants of substrate specificity in RNA-dependent nucleotidyl transferases.
Determinants of substrate specificity in RNA-dependent nucleotidyl transferases.
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DOI：
10.1016/j.bbagrm.2007.12.003
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发表时间：
2008-04
期刊：
影响因子：
--
通讯作者：
G. Martin;S. Doublié;W. Keller
中科院分区：
文献类型：
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作者：
G. Martin;S. Doublié;W. Keller
Poly（A）聚合酶在近50年前被鉴定为将多个AMP残基添加到引物RNA的3′端而不使用来自ATP的模板作为共底物并释放焦磷酸的酶。基于催化结构域中的特征基序的序列同源性，聚（A）聚合酶后来被发现属于作用于非常多样化的底物阵列的核苷酸基转移酶的超家族。属于超家族的酶可以将AMP、CMP或UMP的单个核苷酸添加到RNA、抗生素和蛋白质上，也可以将数百个残基的均聚物添加到RNA分子的3′端。最近报道的几种核苷酸转移酶的结构促进了这些非常不同的酶的催化机制的研究。许多CCA添加酶的结构现在已经揭示了在tRNA的3′端形成CCA尾的所有步骤。此外，聚（A）聚合酶和尿苷酰转移酶的结构现在可作为具有引入的核苷酸和RNA引物的二元和三元复合物获得。这些蛋白质中的一些在底物结合后经历显著的构象变化。这被认为是一种诱导适合机制，驱动基板的选择，并导致催化的指示。从最近的三元复合物的结构的见解表明，在选择传入的核苷酸的引物分子的重要作用。
Poly(A) polymerases were identified almost 50 years ago as enzymes that add multiple AMP residues to the 3′ ends of primer RNAs without use of a template from ATP as cosubstrate and with release of pyrophosphate. Based on sequence homology of a signature motif in the catalytic domain, poly(A) polymerases were later found to belong to a superfamily of nucleotidyl transferases acting on a very diverse array of substrates. Enzymes belonging to the superfamily can add from single nucleotides of AMP, CMP or UMP to RNA, antibiotics and proteins but also homopolymers of many hundred residues to the 3′ ends of RNA molecules. The recently reported structures of several nucleotidyl transferases facilitate the study of the catalytic mechanisms of these very diverse enzymes. Numerous structures of CCA-adding enzymes have now revealed all steps in the formation of a CCA tail at the 3′ end of tRNAs. In addition, structures of poly(A) polymerases and uridylyl transferases are now available as binary and ternary complexes with incoming nucleotide and RNA primer. Some of these proteins undergo significant conformational changes after substrate binding. This is proposed to be an indication for an induced fit mechanism that drives substrate selection and leads to catalysis. Insights from recent structures of ternary complexes indicate an important role for the primer molecule in selecting the incoming nucleotide.