Nair Deepak T, Johnson Robert E, Prakash Louise, Prakash Satya, Aggarwal Aneel K
Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA.
Structure. 2006 Apr;14(4):749-55. doi: 10.1016/j.str.2006.01.010.
Substrate-induced conformational change of the protein is the linchpin of enzymatic reactions. Replicative DNA polymerases, for example, convert from an open to a closed conformation in response to dNTP binding. Human DNA polymerase-iota (hPoliota), a member of the Y family of DNA polymerases, differs strikingly from other polymerases in its much higher proficiency and fidelity for nucleotide incorporation opposite template purines than opposite template pyrimidines. We present here a crystallographic analysis of hPoliota binary complexes, which together with the ternary complexes show that, contrary to replicative DNA polymerases, the DNA, and not the polymerase, undergoes the primary substrate-induced conformational change. The incoming dNTP "pushes" templates A and G from the anti to the syn conformation dictated by a rigid hPoliota active site. Together, the structures posit a mechanism for template selection wherein dNTP binding induces a conformational switch in template purines for productive Hoogsteen base pairing.
蛋白质的底物诱导构象变化是酶促反应的关键。例如，复制性DNA聚合酶会响应dNTP结合而从开放构象转变为封闭构象。人类DNA聚合酶ι（hPoliota）是DNA聚合酶Y家族的成员，与其他聚合酶显著不同的是，它在掺入与模板嘌呤相对的核苷酸时比掺入与模板嘧啶相对的核苷酸时具有更高的效率和保真度。我们在此展示了hPoliota二元复合物的晶体学分析，该分析与三元复合物一起表明，与复制性DNA聚合酶相反，发生主要底物诱导构象变化的是DNA而非聚合酶。进入的dNTP将模板A和G从由刚性hPoliota活性位点决定的反式构象“推”到顺式构象。这些结构共同提出了一种模板选择机制，其中dNTP结合诱导模板嘌呤发生构象转换以形成有效的Hoogsteen碱基对。
