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Updated: Apr 27, 2026

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation
Published on: January 9, 2019
Interaction of structural core protein of classical swine fever virus with endoplasmic reticulum-associated
D P Gladue1, V O'Donnell1, I J Fernandez-Sainz1
1Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
Abstract:
Classical swine fever virus (CSFV) Core protein is involved in virus RNA protection, transcription regulation and virus virulence. To discover additional Core protein functions a yeast two-hybrid system was used to identify host proteins that interact with Core. Among the identified host proteins, the osteosarcoma amplified 9 protein (OS9) was further studied. Using alanine scanning mutagenesis, the OS9 binding site in the CSFV Core protein was identified, between Core residues (90)IAIM(93), near a putative cleavage site. Truncated versions of Core were used to show that OS9 binds a polypeptide representing the 12 C-terminal Core residues. Cells transfected with a double-fluorescent labeled Core construct demonstrated that co-localization of OS9 and Core occurred only on unprocessed forms of Core protein. A recombinant CSFV containing Core protein where residues (90)IAIM(93) were substituted by alanines showed no altered virulence in swine, but a significant decreased ability to replicate in cell cultures.
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