Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560 012, India.
Sci Rep. 2021 Oct 25;11(1):21023. doi: 10.1038/s41598-021-00172-2.
The structures of a cyanophage small heat shock protein (sHSP) were determined as octahedrons of 24-mers and 48-mers and as icosahedrons of 60-mers. An N-terminal deletion construct of an 18 kDa sHSP of Synechococcus sp. phage S-ShM2 crystallized as a 24-mer and its structure was determined at a resolution of 7 Å. The negative stain electron microscopy (EM) images showed that the full-length protein is a mixture of a major population of larger and a minor population of smaller cage-like particles. Their structures have been determined by electron cryomicroscopy 3D image reconstruction at a resolution of 8 Å. The larger particles are 60-mers with icosahedral symmetry and the smaller ones are 48-mers with octahedral symmetry. These structures are the first of the viral/phage origin and the 60-mer is the largest and the first icosahedral assembly to be reported for sHSPs.
该病毒的一个小热休克蛋白（sHSP）的结构确定为 24 聚体和 48 聚体的八面体和 60 聚体的二十面体。Synechococcus sp. 噬菌体 S-ShM2 的一个 18 kDa sHSP 的 N 端缺失构建体结晶为 24 聚体，其结构在 7 Å 的分辨率下确定。负染色电子显微镜（EM）图像显示，全长蛋白是较大和较小笼状颗粒的主要群体和较小群体的混合物。它们的结构已通过电子 cryomicroscopy 3D 图像重建在 8 Å 的分辨率下确定。较大的颗粒是具有二十面体对称性的 60 聚体，较小的颗粒是具有八面体对称性的 48 聚体。这些结构是病毒/噬菌体起源的第一个结构，60 聚体是最大的，也是第一个报道的 sHSP 的二十面体组装体。
