Bovine Papillomavirus CryoEM Image Data

Papillomaviruses, members of a group of dsDNA viruses associated with epithelial growths and tumors, have compact capsids assembled from 72 pentamers of the protein L1. We have determined the structure of bovine papillomavirus by electron cryomicrosopy (cryoEM), at ∼3.6 Å resolution. The density map, obtained from single-particle analysis of ∼4,000 particle images, shows the trace of the L1 polypeptide chain and reveals how the N- and C-terminal “arms” of a subunit (extensions from its β-jelly-roll core) associate with a neighboring pentamer. Critical contacts come from the C-terminal arm, which loops out from the core of the subunit, forms contacts (including a disulfide) with two subunits in a neighboring pentamer, and reinserts into the pentamer from which it emanates. This trace corrects one feature of an earlier model. We discuss implications of the structure for virion assembly and for pathways of infectious viral entry. We suggest that it should be possible to obtain image reconstructions of comparable resolution from cryoEM images of asymmetric particles. From the work on papillomavirus described here, we estimate that such a reconstruction will require about 1.5 million images to achieve the same number of averaged asymmetric units; structural variability will increase this number substantially.Data descriptionLinked at right is a stack (16 GB) of 5,546 images (MRC/CCP4 format) of bovine papillomavirus (BPV [1]) collected at 300 kV and a calibrated magnification of 56,588, giving a pixel size on the specimen of 1.237 Å. Alignment parameters determined by Frealign for each particle in the stack can also be found below, as well as a reconstruction of BPV (also MRC/CCP4 format). Ewald sphere and beamtilt correction were performed. The atomic coordinates contain the coordinates from one subunit (3IYJ.pdb) and the five surrounding subunits to enable exploration of inter-subunit contacts.

乳头瘤病毒（Papillomaviruses）属于双链脱氧核糖核酸（dsDNA）病毒类群，与上皮增生及肿瘤发生密切相关，其衣壳结构紧凑，由72个L1蛋白五聚体组装而成。本研究通过冷冻电子显微镜（cryoEM）解析了牛乳头瘤病毒的结构，分辨率约为3.6埃（Å）。该密度图源自约4000个颗粒图像的单颗粒分析，清晰显示了L1多肽链的骨架走向，并揭示了亚基的N端与C端“臂”（源自其β果冻卷（β-jelly-roll）核心的延伸区域）如何与相邻五聚体相互作用。关键的相互作用由C端臂介导：该臂从亚基核心伸出，与相邻五聚体内的两个亚基形成相互作用（包括二硫键），随后重新插入其起源的五聚体中。本次解析的骨架走向修正了此前模型中的一处错误。我们讨论了该结构对于病毒衣壳组装以及感染性病毒入侵途径的研究意义。本研究表明，通过非对称颗粒的冷冻电镜图像获取相当分辨率的图像重构是可行的。基于本次针对乳头瘤病毒的研究，我们估算该类重构若要获得同等数量的平均化非对称单元，约需要150万张图像；而结构异质性将大幅提升所需的图像数量。
数据集说明：右侧链接包含一个大小为16GB的图像栈，内含5546张牛乳头瘤病毒（BPV [1]）的冷冻电镜图像，格式为MRC/CCP4。该数据采集于300kV加速电压下，标定放大倍数为56588倍，样本层面的像素尺寸为1.237埃（Å）。本图像栈中每个颗粒的Frealign比对参数，以及牛乳头瘤病毒的三维重构模型（同样为MRC/CCP4格式）均可在下方获取。实验中已完成埃瓦尔德球（Ewald sphere）校正与束倾斜校正。本次提供的原子坐标包含一个亚基（3IYJ.pdb）及其周围五个亚基的坐标，便于研究亚基间的相互作用。