Zhang W, Olson N H, Baker T S, Faulkner L, Agbandje-McKenna M, Boulton M I, Davies J W, McKenna R
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
Virology. 2001 Jan 20;279(2):471-7. doi: 10.1006/viro.2000.0739.
The Geminiviridae is an extensive family of plant viruses responsible for economically devastating diseases in crops worldwide. Geminiviruses package circular, single-stranded DNA (ssDNA) genomes. The characteristic twinned or "geminate" particles, which consist of two joined, incomplete T = 1 icosahedra, are unique among viruses. We have determined the first structure of a geminivirus particle, the Nigerian strain of Maize streak virus (MSV-N), using cryo-electron microscopy and three-dimensional image reconstruction methods. The particle, of dimensions 220 x 380 A, has an overall 52-point-group symmetry, in which each half particle "head" consists of the coat protein (CP) arranged with quasi-icosahedral symmetry. We have modeled the MSV-N CP as an eight-stranded, antiparallel beta-barrel motif (a structural motif common to all known ssDNA viruses) with an N-terminal alpha-helix. This has produced a model of the geminate particle in which 110 copies of the CP nicely fit into the reconstructed density map. The reconstructed density map and MSV-N pseudo-atomic model demonstrate that the geminate particle has a stable, defined structure.
双生病毒科是一个庞大的植物病毒家族，可引发全球范围内农作物的经济毁灭性病害。双生病毒包裹着环状单链DNA（ssDNA）基因组。其特征性的孪生或“双生”颗粒由两个相连的、不完整的T = 1二十面体组成，在病毒中独一无二。我们利用冷冻电子显微镜和三维图像重建方法，确定了双生病毒颗粒的首个结构，即玉米条纹病毒尼日利亚株（MSV-N）的结构。该颗粒尺寸为220×380埃，具有整体的52点群对称性，其中每个半颗粒“头部”由具有准二十面体对称性排列的外壳蛋白（CP）组成。我们将MSV-N CP建模为具有N端α螺旋的八链反平行β桶基序（这是所有已知ssDNA病毒共有的结构基序）。这产生了一个双生颗粒模型，其中110个CP拷贝很好地拟合到重建的密度图中。重建的密度图和MSV-N伪原子模型表明，双生颗粒具有稳定、明确的结构。
