Hydrolytic editing by a class II aminoacyl-tRNA synthetase
Hydrolytic editing by a class II aminoacyl-tRNA synthetase
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DOI：
10.1073/pnas.97.16.8916
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发表时间：
2000-08-01
影响因子：
11.1
通讯作者：
Musier-Forsyth, K
中科院分区：
文献类型：
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作者：
Beuning, PJ;Musier-Forsyth, K
由氨基酰-tRNA合成酶催化的编辑反应是准确翻译遗传密码的关键。到目前为止，这种活性，即未激活的氨基酸在转移到非同源tRNAs之前或之后被水解，仅在I类合成酶的情况下得到了广泛的表征。II类合成酶具有与I类完全不同的活性部位结构，因此，I类合成酶编辑的研究结果可能不适用于II类酶。第二类大肠埃希菌Pro-tRNA合成酶在转移到tRNA(Pro)之前失活丙氨酸和水解非同源氨基酸。这种酶还能够快速脱酰化错误充电的Ala-tRNA(Pro)变体。位于II类特异基序3共有序列中的一个半胱氨酸残基(C443)对于Pro-tRNA合成酶的氨酰化活性是不必要的。我们在这里表明，C443在这个II类合成酶对Ala-tRNA(Pro)的水解性编辑中是关键的。
Editing reactions catalyzed by aminoacyl-tRNA synthetases are critical for accurate translation of the genetic code. To date, this activity, whereby misactivated amino acids are hydrolyzed either before or after transfer to noncognate tRNAs, has been characterized extensively only in the case of class I synthetases. Class II synthetases have an active-site architecture that is completely distinct from that of class I. Thus, findings on editing by class I synthetases may not be applicable generally to class II enzymes. Class II Escherichia coli proline-tRNA synthetase is shown here to misactivate alanine and to hydrolyze the noncognate amino acid before transfer to tRNA(Pro). This enzyme also is capable of rapidly deacylating a mischarged Ala-tRNA(Pro) variant. A single cysteine residue (C443) that is located within the class II-specific motif 3 consensus sequence was shown previously to be dispensable for proline-tRNA synthetase aminoacylation activity. We show here that C443 is critical for the hydrolytic editing of Ala-tRNA(Pro) by this class II synthetase.