Hexameric Viral RNA Helicases
Hexameric Viral RNA Helicases
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DOI：
10.1039/9781849732215-00213
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发表时间：
2010-01-01
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影响因子：
--
通讯作者：
Tuma, Roman
中科院分区：
文献类型：
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作者：
Tuma, Roman
六聚体解旋酶广泛存在于DNA复制中（如DnaB，大肠杆菌中主要的复制解旋酶）。大肠杆菌）。六聚体RNA解旋酶完成从转录终止到病毒复制和组装的各种功能。与普遍存在的SF2解旋酶相反，只有少数特征性的六聚体解旋酶解旋或易位RNA。大多数六聚体解旋酶由围绕中央通道排列成环的相同亚基组成。六个相同的ATP结合位点位于亚基界面在环的周边，并涵盖来自相邻亚基的残基。中央通道具有核酸结合位点，这是解旋酶活性所必需的。尽管细节仍在讨论中，但解旋的机制很可能涉及沿着结合在中央通道内的核酸链沿着移位，而互补链被环排除在外（图9.1（A））。[1]易位链的拓扑外壳以类似于复制型DNA钳（如PCNA）的方式确保了持续合成能力。事实上，结构比较表明，持续合成能力钳从六聚体分子马达通过结合和水解ATP的能力的损失。2
Hexameric helicases are widespread in DNA replication (eg, DnaB, the main replicative helicase in E. coli). Hexameric RNA helicases fulfill various functions ranging from transcription termination to virus replication and assembly. In contrast to the ubiquitous SF2 helicases there are only a few characterised hexameric helicases that unwind or translocate RNA. Most hexameric helicases are composed of identical subunits arranged into a ring around the central channel. Six identical ATP binding sites are located at subunit interfaces at the perimeter of the ring and encompass residues from neighbouring subunits. The central channel hosts nucleic-acid-binding sites, which are essential for helicase activity. While details are still being debated, the mechanism of unwinding most likely involves translocation along a nucleic acid strand bound within the central channel while the complementary strand is excluded by the ring (Figure 9.1 (A)). 1 The topological enclosure of the translocated strand assures processivity in a fashion similar to replicative DNA clamps, such as PCNA. Indeed, structural comparisons suggest that processivity clamps evolved from hexameric molecular motors through the loss of the ability to bind and hydrolyse ATP. 2