Crystal structures of a template-independent DNA polymerase:: murine terminal deoxynucleotidyltransferase
Crystal structures of a template-independent DNA polymerase:: murine terminal deoxynucleotidyltransferase
复制标题
DOI：
10.1093/emboj/21.3.427
复制
发表时间：
2002-02-01
期刊：
影响因子：
11.4
通讯作者：
Papanicolaou, C
中科院分区：
文献类型：
--
作者：
Delarue, M;Boulé, JB;Papanicolaou, C
小鼠末端脱氧核苷酸转移酶（TdT）催化核的晶体结构在2.35埃分辨率下显示出典型的DNA聚合酶β样折叠锁定在封闭形式。此外，两种不同的二元配合物的结构，一种是寡核苷酸引物，另一种是ddATP-Co2+配合物，表明底物和催化位点的两个二价离子在TdT中的定位方式与人类DNA聚合酶β三元配合物相似，表明这两种蛋白质中核苷酸转移的共同金属离子机制。TdT无法容纳模板链可以解释为催化位点的空间位阻，这是由长lariat样环引起的，这在DNA聚合酶β中是不存在的。然而，这种区分环的位移将足以揭示一些进化上保守的残基，这些残基随后可以与模板DNA链相互作用。目前的结构可以用来模拟最近发现的人类聚合酶mu，它具有43%的序列同一性。
The crystal structure of the catalytic core of murine terminal deoxynucleotidyltransferase (TdT) at 2.35 Angstrom resolution reveals a typical DNA polymerase beta-like fold locked in a closed form. In addition, the structures of two different binary complexes, one with an oligonucleotide primer and the other with an incoming ddATP-Co2+ complex, show that the substrates and the two divalent ions in the catalytic site are positioned in TdT in a manner similar to that described for the human DNA polymerase beta ternary complex, suggesting a common two metal ions mechanism of nucleotidyl transfer in these two proteins. The inability of TdT to accommodate a template strand can be explained by steric hindrance at the catalytic site caused by a long lariat-like loop, which is absent in DNA polymerase beta. However, displacement of this discriminating loop would be sufficient to unmask a number of evolutionarily conserved residues, which could then interact with a template DNA strand. The present structure can be used to model the recently discovered human polymerase mu, with which it shares 43% sequence identity.