Limited proteolysis of SARS-CoV-2 Spike treated at pH 2 or pH 7

SARS-CoV-2 is a respiratory virus spreading via aerosol particles. Aerosol particles can exhibit extreme environmental conditions affecting contained viruses, including acidic pH. Here, we study how harsh pH conditions, such as pH 2, can affect the structure of Spike, which is the main protein mediating viral entry into host cells. By performing limited proteolysis with the unspecific protease K coupled to mass spectrometry, we identified 4 semi-tryptic peptides in the S2 subdomain of spike. These results indicate structural changes in the S2 subdomain induced by treatment at pH 2.