Department of Biological Science, Florida State University, Biology Unit I, 230A, 91 Chieftan Way, Tallahassee, FL, 32306-4370, United States; Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306-4370, United States.
Department of Biological Science, Florida State University, Biology Unit I, 230A, 91 Chieftan Way, Tallahassee, FL, 32306-4370, United States.
Virology. 2014 Feb;450-451:205-12. doi: 10.1016/j.virol.2013.11.019. Epub 2014 Jan 6.
ΦM12 is the first example of a T=19l geometry capsid, encapsulating the recently sequenced genome. Here, we present structures determined by cryo-EM of full and empty capsids. The structure reveals the pattern for assembly of 1140 HK97-like capsid proteins, pointing to interactions at the pseudo 3-fold symmetry axes that hold together the asymmetric unit. The particular smooth surface of the capsid, along with a lack of accessory coat proteins encoded by the genome, suggest that this interface is the primary mechanism for capsid assembly. Two-dimensional averages of the tail, including the neck and baseplate, reveal that ΦM12 has a relatively narrow neck that attaches the tail to the capsid, as well as a three-layer baseplate. When free from DNA, the icosahedral edges expand by about 5nm, while the vertices stay at the same position, forming a similarly smooth, but bowed, T=19l icosahedral capsid.
ΦM12 是首个 T=19l 几何形状衣壳的实例，它包被了最近测序的基因组。在此，我们展示了通过冷冻电镜对完整和空衣壳进行结构测定的结果。该结构揭示了 1140 个 HK97 样衣壳蛋白组装的模式，指向在伪 3 倍对称轴处的相互作用，这些作用将非对称单位保持在一起。衣壳的特殊光滑表面，以及基因组编码的辅助外壳蛋白的缺乏，表明该界面是衣壳组装的主要机制。尾部的二维平均值，包括颈部和基板，表明 ΦM12 具有相对较窄的颈部，将尾部连接到衣壳上，以及三层基板。当游离于 DNA 时，二十面体边缘扩张约 5nm，而顶点保持在相同位置，形成一个类似的光滑但弯曲的 T=19l 二十面体衣壳。
