A Cut above the Rest: Characterization of the Assembly of a Large Viral Icosahedral Capsid
Mohd Redzuan, N.H.
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AbstractThe head of Salmonella virus SPN3US is composed of ?50 different proteins and is unusual because within its packaged genome there is a mass (>40 MDa) of ejection or E proteins that enter the Salmonella cell. The assembly mechanisms of this complex structure are poorly understood. Previous studies showed that eight proteins in the mature SPN3US head had been cleaved by the prohead protease. In this study, we present the characterization of SPN3US prohead protease mutants using transmission electron microscopy and mass spectrometry. In the absence of the prohead protease, SPN3US head formation was severely impeded and proheads accumulated on the Salmonella inner membrane. This impediment is indicative of proteolysis being necessary for the release and subsequent DNA packaging of proheads in the wild-type phage. Proteomic analyses of gp245- proheads that the normal proteolytic processing of head proteins had not occurred. Assays of a recombinant, truncated form of the protease found it was active, leading us to hypothesize that the C-terminal propeptide has a role in targeting the protease into the prohead core. Our findings provide new evidence regarding the essential role of proteolysis for correct head assembly in this remarkable parasite. Copyright 2020 by the authors.
SponsorsFunding: Research reported in this publication was supported by the Thomas H. Gosnell School of Life Sciences and the National Institute of General Medical Sciences of the National Institutes of Health under Award Number UA5GM126533 (JAT) and R15GM120653 (AOH). LWB was supported by NIH award number R01 GM11876. The UTHSCSA Institutional Mass Spectrometry Laboratory was supported in part by UTHSCSA and NIH grant 1S10RR025111-01 for purchase of the Orbitrap mass spectrometer (STW).
transmission electron microscopy
Identifier to cite or link to this itemhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85087659456&doi=10.3390%2fv12070725&partnerID=40&md5=c40a7aa0f2ad8f6505f70705a6b267af; http://hdl.handle.net/10713/13373