RNA packaging device of double-stranded RNA bacteriophages, possibly as simple as hexamer of P4 protein
RNA packaging device of double-stranded RNA bacteriophages, possibly as simple as hexamer of P4 protein
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DOI：
10.1074/jbc.m306928200
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发表时间：
2003-11-28
影响因子：
4.8
通讯作者：
Makeyev, EV
中科院分区：
文献类型：
--
作者：
Kainov, DE;Pirttimaa, M;Makeyev, EV
复杂病毒的基因组已被证明，在许多情况下，被包装到预先形成的空衣壳（原衣壳）。该反应通过分子马达以NTP水解为代价逆浓度梯度移位核酸来进行。目前，由于包装马达的复杂性，包装的分子机制仍然难以捉摸。在来自囊病毒科的双链RNA噬菌体phi 6的情况下，单链基因组前体的包装需要六聚体NTR，P4。在本研究中，纯化的P4蛋白从其他两个囊病毒，phi 8和phi 13，其特征在于，并与phi 6 P4。所有三种蛋白质都是具有α/β折叠的六聚体单链RNA刺激的NTPases。使用直接马达测定，我们发现phi 8和phi 13 P4六聚体沿着ssRNA从5'易位到沿着3'，而phi 6 P4的类似活性需要与原衣壳结合。这种差异可以通过phi 8和phi 13 P4对核酸的固有高亲和力来解释。单向易位导致RNA解旋酶活性。因此，囊病毒科的P4蛋白与六聚体解旋酶表现出广泛的相似性，是研究病毒包装马达机制的简单模型。
Genomes of complex viruses have been demonstrated, in many cases, to be packaged into preformed empty capsids (procapsids). This reaction is performed by molecular motors translocating nucleic acid against the concentration gradient at the expense of NTP hydrolysis. At present, the molecular mechanisms of packaging remain elusive due to the complex nature of packaging motors. In the case of the double-stranded RNA bacteriophage phi6 from the Cystoviridae family, packaging of single-stranded genomic precursors requires a hexameric NTPase, P4. In the present study, the purified P4 proteins from two other cystoviruses, phi8 and phi13, were characterized and compared with phi6 P4. All three proteins are hexameric, single-stranded RNA-stimulated NTPases with alpha/beta folds. Using a direct motor assay, we found that phi8 and phi13 P4 hexamers translocate 5' to 3' along ssRNA, whereas the analogous activity of phi6 P4 requires association with the procapsid. This difference is explained by the intrinsically high affinity of phi8 and phi13 P4s for nucleic acids. The unidirectional translocation results in RNA helicase activity. Thus, P4 proteins of Cystoviridae exhibit extensive similarity to hexameric helicases and are simple models for studying viral packaging motor mechanisms.