The dTTPase mechanism of T7 DNA helicase resembles the binding change mechanism of the F-1-ATPase
The dTTPase mechanism of T7 DNA helicase resembles the binding change mechanism of the F-1-ATPase
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DOI：
10.1073/pnas.94.10.5012
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发表时间：
1997-05-13
影响因子：
11.1
通讯作者：
Patel, SS
中科院分区：
文献类型：
--
作者：
Hingorani, MM;Washington, MT;Patel, SS
噬菌体T7 DNA解旋酶是一种环状的六聚体，它利用dTTP水解作为能量来源催化双链体DNA解旋。在六聚体上的六个潜在的核苷酸结合位点中，我们发现三个是非催化位点，三个是催化位点。非催化位点以高亲和力结合核苷酸，但结合到这些位点的dTTP不会通过催化位点处的许多dTTP周转而解离或水解。催化位点表现出很强的协同作用，导致dTTP的顺序结合和水解。已阐明的T7解旋酶催化位点的dTTT转换机制与ATP合酶的结合变化机制非常相似。基于这种相似性，提出了六聚体解旋酶的一般机制。在这个机制中，F1-ATP酶样的旋转运动的单链DNA，这是通过六聚体的中心孔结合，提出了导致单向移位沿着单链DNA和双链体DNA解旋。
Bacteriophage T7 DNA helicase is a ring-shaped hexamer that catalyzes duplex DNA unwinding using dTTP hydrolysis as an energy source. Of the six potential nucleotide binding sites on the hexamer, we have found that three are noncatalytic sites and three are catalytic sites. The noncatalytic sites bind nucleotides with a high affinity, but dTTPs bound to these sites do not dissociate or hydrolyze through many dTTPase turnovers at the catalytic sites. The catalytic sites show strong cooperativity which leads to sequential binding and hydrolysis of dTTP. The elucidated dTTPase mechanism of the catalytic sites of T7 helicase is remarkably similar to the binding change mechanism of the ATP synthase, Based on the similarity, a general mechanism for hexameric helicases is proposed. In this mechanism, an F1-ATPase-like rotational movement around the single-stranded DNA, which is bound through the central hole of the hexamer, is proposed to lead to unidirectional translocation along single-stranded DNA and duplex DNA unwinding.