Multiple nanocages of a cyanophage small heat shock protein with icosahedral and octahedral symmetries.
Biswas, S., Garg, P., Dutta, S., Suguna, K.(2021) Sci Rep 11: 21023-21023
- PubMed: 34697325 
- DOI: https://doi.org/10.1038/s41598-021-00172-2
- Primary Citation of Related Structures:  
7CK4 - PubMed Abstract: 
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.
Organizational Affiliation: 
Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560 012, India.