Crystal structure of T7 gene 4 ring helicase indicates a mechanism for sequential hydrolysis of nucleotides
Crystal structure of T7 gene 4 ring helicase indicates a mechanism for sequential hydrolysis of nucleotides
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DOI：
10.1016/s0092-8674(00)80871-5
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发表时间：
2000-06-09
期刊：
影响因子：
64.5
通讯作者：
Wigley, DB
中科院分区：
文献类型：
--
作者：
Singleton, MR;Sawaya, MR;Wigley, DB
我们已经确定了晶体结构的arl活性，六聚体片段的基因4解旋酶从噬菌体T7。该结构揭示了亚基接触如何稳定六聚体。偏离预期的六重对称性的六聚体表明，该结构是一个中间体的催化途径。结构的不对称性的后果建议一个“结合变化”的机制来解释如何合作的结合和水解的核苷酸耦合到最有可能伴随双链体解旋的环中的构象变化。与一个nonhydrolyzable ATP类似物的复合物的结构提供了额外的证据，这一假设，只有四个六个可能的核苷酸结合位点被占领在这种构象的六聚体。该模型提出了DNA易位的机制。
We have determined the crystal structure of arl active, hexameric fragment of the gene 4 helicase from bacteriophage T7. The structure reveals how subunit contacts stabilize the hexamer. Deviation from expected six-fold symmetry of the hexamer indicates that the structure is of an intermediate on the catalytic pathway. The structural consequences of the asymmetry suggest a "binding change" mechanism to explain how cooperative binding and hydrolysis of nucleotides are coupled to conformational changes in the ring that most likely accompany duplex unwinding. The structure of a complex with a nonhydrolyzable ATP analog provides additional evidence for this hypothesis, with only four of the six possible nucleotide binding sites being occupied in this conformation of the hexamer. This model suggests a mechanism for DNA translocation.