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Publication Abstract from PubMed

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 delta protein that shares no homology with any other proteins. delta can be expressed either as a free delta or a CP-delta fusion protein by ribosomal frameshift, but the structure and function of both delta and CP-delta remain unknown. Using a combination of electron microscopy, X-ray crystallography, computational and biophysical analyses, here we show that the Orsay delta protein forms a ~420-A long, pentameric fiber with an N-terminal alpha-helical bundle, a beta-stranded filament in the middle, and a C-terminal head domain. The pentameric nature of the delta fiber has been independently confirmed by both mass spectrometry and analytical ultracentrifugation. Recombinant Orsay capsid containing CP-delta shows protruding long fibers with globular heads at the distal end. Mutant viruses with disrupted CP-delta 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 delta proteins to worm culture greatly reduced Orsay infectivity in a sequence-specific manner. Based on the structure resemblance between the Orsay CP-delta fiber and the fibers from reovirus and adenovirus, we propose that CP-delta functions as a cell attachment protein to mediate Orsay entry into worm intestine cells.

Structure of a pentameric virion-associated fiber with a potential role in Orsay virus entry to host cells.,Fan Y, Guo YR, Yuan W, Zhou Y, Holt MV, Wang T, Demeler B, Young NL, Zhong W, Tao YJ PLoS Pathog. 2017 Feb 27;13(2):e1006231. doi: 10.1371/journal.ppat.1006231., eCollection 2017 Feb. PMID:28241071^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.