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Updated: Oct 3, 2025

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation
Published on: January 9, 2019
Cryptococcal Protease(s) and the Activation of SARS-CoV-2 Spike (S) Protein
Nozethu Mjokane1, Maphori Maliehe1, Olufemi S Folorunso1
1Department of Microbiology and Biochemistry, University of the Free State, 205 Nelson Mandela Drive, Park West, Bloemfontein 9301, South Africa.
Abstract:
In this contribution, we report on the possibility that cryptococcal protease(s) could activate the SARS-CoV-2 spike (S) protein. The S protein is documented to have a unique four-amino-acid sequence (underlined, SPRRAR↓S) at the interface between the S1 and S2 sites, that serves as a cleavage site for the human protease, furin. We compared the biochemical efficiency of cryptococcal protease(s) and furin to mediate the proteolytic cleavage of the S1/S2 site in a fluorogenic peptide. We show that cryptococcal protease(s) processes this site in a manner comparable to the efficiency of furin (p > 0.581). We conclude the paper by discussing the impact of these findings in the context of a SARS-CoV-2 disease manifesting while there is an underlying cryptococcal infection.
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