Inside the virions of α-herpesviruses, tegument protein pUL25 anchors the tegument to capsid vertices through direct interactions with tegument proteins pUL17 and pUL36. In addition to promoting virion assembly, both pUL25 and pUL36 are critical for intracellular microtubule-dependent capsid transport. Despite these essential roles during infection, the stoichiometry and precise organization of pUL25 and pUL36 on the capsid surface remain controversial due to the insufficient resolution of existing reconstructions from cryo-electron microscopy (cryoEM). Here, we report a threedimensional (3D) icosahedral reconstruction of pseudorabies virus (PRV), a varicellovirus of the α-herpesvirinae subfamily, obtained by electron-counting cryoEM at 4.9 Å resolution. Our reconstruction resolves a dimer of pUL25 forming a capsidassociated tegument complex with pUL36 and pUL17 through a coiled coil helix bundle, thus correcting previous misinterpretations. A comparison between reconstructions of PRV and the γ-herpesvirus Kaposi’s sarcoma-associated herpesvirus (KSHV) reinforces their similar architectures and establishes important subfamily differences in the capsid-tegument interface.
Bibliographical noteFunding Information:
This research was supported in part by grants from the US National Institutes of Health (R01 AI056346 to G. A. S.), the NSFC (313290002 to Z. H. Z.) and the CAS (XDB02050000 to G. Q. B.). We acknowledge the use of instruments at the Electron Imaging Center for Nanoma-chines supported by UCLA and by instrumentation grants from NIH (1S10RR23057) and NSF (DBI-1338135). The cryoEM density map has been deposited in the EM Data Bank under the accession codes EMD-8760.
© 2017 The Authors.
- PUL25 dimer
- PUL36 (VP1/2)
- Pseudorabies virus
- Tegument proteins