[转移贴]Structure：噬菌体29的组装过程
原贴由Rojjer 发表于 2008-9-21 11:01http://biosky.haotui.com/thread-6502-1-3.html
带尾噬菌体的形态一般从一个空衣壳或者原衣壳开始组装，然后噬菌体基因组插入到这个预备蛋白壳中。基因组包装的过程要考虑熵和静电的作用，以及DNA必须克服的弯曲能。事实上，噬菌体DNA的装运泵是众所周知的最强大的生物泵。装运一般由一个分子马达驱动，将ATP水解得到的能量转换为DNA的运动能量。
8月6日《结构》（Structure）杂志的封面文章，报道了Morais等人描绘的噬菌体29DNA装运泵不同部分的分子排列与分子衣壳的情况。已有的研究数据表明，低温电子显微镜可以描绘出噬菌体29的DNA装运泵的相对位置，12重对称的头-尾连接器的分子边界，以及5重对称的pRNA、供能的ATP酶和分子衣壳。
Morais等人发现，分子改造可能由5重对称体构成，包括含174碱基、120碱基和71碱基等等。这些结构与pRNA和ATP酶在原衣壳的顶端周围形成的五聚体泵部分一致。所这些研究成果表明了装运泵的组装途径与DNA移动到空的原衣壳中的分子机制。
Structure，Vol 16, 1267-1274, 06 August 2008，Marc C. Morais, Michael G. Rossmann
Defining Molecular and Domain Boundaries in the Bacteriophage 29 DNA Packaging Motor
Marc C. Morais, Jaya S. Koti,Valorie D. Bowman,Emilio Reyes-Aldrete,Dwight L. Anderson,and Michael G. Rossmann
Cryo-electron microscopy (cryo-EM) studies of the bacteriophage 29 DNA packaging motor have delineated the relative positions and molecular boundaries of the 12-fold symmetric head-tail connector, the 5-fold symmetric prohead RNA (pRNA), the ATPase that provides the energy for packaging, and the procapsid. Reconstructions, assuming 5-fold symmetry, were determined for proheads with 174-base, 120-base, and 71-base pRNA; proheads lacking pRNA; proheads with ATPase bound; and proheads in which the packaging motor was missing the connector. These structures are consistent with pRNA and ATPase forming a pentameric motor component around the unique vertex of proheads. They suggest an assembly pathway for the packaging motor and a mechanism for DNA translocation into empty proheads.
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