Structure of pentameric virion-associated fiber with a potential role in Orsay virus entry to host cells

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Fan, Yanlin
Guo, Yusong R.
Yuan, Wang
Zhou, Ying
Holt, Matthew V.
Wang, Tao
Demeler, Borries
Young, Nicolas L.
Zhong, Weiwei
Tao, Yizhi J.
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Public Library of Science
Despite the wide use of Caenorhabditis elegans as a model organism, the first virus naturally infecting this organism was not discovered until six years ago. The Orsay virus and its related nematode viruses have a positive-sense RNA genome, encoding three proteins: CP, RdRP, and a novel δ protein that shares no homology with any other proteins. δ can be expressed either as a free δ or a CP-δ fusion protein by ribosomal frameshift, but the structure and function of both δ and CP-δ remain unknown. Using a combination of electron microscopy, X-ray crystallography, computational and biophysical analyses, here we show that the Orsay δ protein forms a ~420-Å long, pentameric fiber with an N-terminal α-helical bundle, a β-stranded filament in the middle, and a C-terminal head domain. The pentameric nature of the δ fiber has been independently confirmed by both mass spectrometry and analytical ultracentrifugation. Recombinant Orsay capsid containing CP-δ shows protruding long fibers with globular heads at the distal end. Mutant viruses with disrupted CP-δ fibers were generated by organism-based reverse genetics. These viruses were found to be either non-viable or with poor infectivity according to phenotypic and qRT-PCR analyses. Furthermore, addition of purified δ proteins to worm culture greatly reduced Orsay infectivity in a sequence-specific manner. Based on the structure resemblance between the Orsay CP-δ fiber and the fibers from reovirus and adenovirus, we propose that CP-δ functions as a cell attachment protein to mediate Orsay entry into worm intestine cells.
Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) applies
Orsay , Crystal structure , Pentameric
Fan, Y., Guo, Y. R., Yuan, W., Zhou, Y., Holt, M. V., Wang, T., Demeler, B., Young, N. L., Zhong, W., & Tao, Y. J. (2017). Structure of a pentameric virion-associated fiber with a potential role in Orsay virus entry to host cells. PLoS Pathogens, 13(2), Article e1006231.