Cryo-EM reconstruction of the Cafeteria roenbergensis virus capsid suggests novel
assembly pathway for giant viruses
#MMPMID28710447
Xiao C
; Fischer MG
; Bolotaulo DM
; Ulloa-Rondeau N
; Avila GA
; Suttle CA
Sci Rep
2017[Jul]; 7
(1
): 5484
PMID28710447
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Whereas the protein composition and overall shape of several giant virus capsids
have been described, the mechanism by which these large capsids assemble remains
enigmatic. Here, we present a reconstruction of the capsid of Cafeteria
roenbergensis virus (CroV), one of the largest viruses analyzed by cryo-electron
microscopy (cryo-EM) to date. The CroV capsid has a diameter of 3,000?Å and a
Triangulation number of 499. Unlike related mimiviruses, the CroV capsid is not
decorated with glycosylated surface fibers, but features 30?Å-long surface
protrusions that are formed by loops of the major capsid protein. Based on the
orientation of capsomers in the cryo-EM reconstruction, we propose that the
capsids of CroV and related giant viruses are assembled by a newly conceived
assembly pathway that initiates at a five-fold vertex and continuously proceeds
outwards in a spiraling fashion.
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