The atomic structure of baculovirus polyhedra reveals the independent emergence of infectious crystals in DNA and RNA viruses
The atomic structure of baculovirus polyhedra reveals the independent emergence of infectious crystals in DNA and RNA viruses
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DOI：
10.1073/pnas.0910686106
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发表时间：
2009-12-29
影响因子：
11.1
通讯作者：
Metcalf, Peter
中科院分区：
文献类型：
--
作者：
Coulibaly, Fasseli;Chiu, Elaine;Metcalf, Peter
杆状病毒是普遍存在的昆虫病毒，以其作为生物杀虫剂、基因治疗载体和蛋白质表达系统的用途而众所周知。重组蛋白在昆虫细胞培养物中的过表达利用多角体蛋白基因的强启动子。在受感染的幼虫中，多角体蛋白形成称为多角体的坚固的细胞内晶体，其在环境中长时间保护被包裹的病毒体。多角体由昆虫病毒的两个不相关的家族产生，杆状病毒和胞病毒。cypovirus多角体的原子结构揭示了三聚体的复杂包装，三聚体通过多角体蛋白分子的突出N-末端螺旋臂相互连接。杆状病毒和cypovirus多角体共享几乎相同的晶格，并且另外不相关的杆状病毒多角体蛋白质序列的N-末端区域也被预测为α-螺旋。这些结果表明蛋白质之间的同源性和病毒多角体的共同结构基础。在这里，我们提出了2.2埃结构的杆状病毒多角体确定由X射线晶体学从体内产生的微晶。我们表明，潜在的分子组织，事实上，非常不同。虽然这两个多面体具有几乎相同的晶胞尺寸和共享I23对称性，多面体分子在结构上是不相关的，并在晶体中包装不同。特别地，二硫键和结构域交换的N-末端结构域稳定杆状病毒多角体的构建块，并且互锁的C-末端臂将单位细胞连接在一起。我们发现，N-末端的螺旋臂有不同的结构作用，杆状病毒和cypovirus多角体，并得出结论，有没有一个共同的进化起源为两类多角体的结构证据。
Baculoviruses are ubiquitous insect viruses well known for their use as bioinsecticides, gene therapy vectors, and protein expression systems. Overexpression of recombinant proteins in insect cell culture utilizes the strong promoter of the polyhedrin gene. In infected larvae, the polyhedrin protein forms robust intracellular crystals called polyhedra, which protect encased virions for prolonged periods in the environment. Polyhedra are produced by two unrelated families of insect viruses, baculoviruses and cypoviruses. The atomic structure of cypovirus polyhedra revealed an intricate packing of trimers, which are interconnected by a projecting N-terminal helical arm of the polyhedrin molecule. Baculovirus and cypovirus polyhedra share nearly identical lattices, and the N-terminal region of the otherwise unrelated baculovirus polyhedrin protein sequence is also predicted to be alpha-helical. These results suggest homology between the proteins and a common structural basis for viral polyhedra. Here, we present the 2.2-angstrom structure of baculovirus polyhedra determined by x-ray crystallography from microcrystals produced in vivo. We show that the underlying molecular organization is, in fact, very different. Although both polyhedra have nearly identical unit cell dimensions and share I23 symmetry, the polyhedrin molecules are structurally unrelated and pack differently in the crystals. In particular, disulfide bonds and domain-swapped N-terminal domains stabilize the building blocks of baculovirus polyhedra and interlocking C-terminal arms join unit cells together. We show that the N-terminal projecting helical arms have different structural roles in baculovirus and cypovirus polyhedra and conclude that there is no structural evidence for a common evolutionary origin for both classes of polyhedra.