Deamidation drives molecular aging of the SARS-CoV-2 spike protein receptor-binding motif

LORENZO, RAMIRO; DEFELIPE, LUCAS A.; ALIPERTI, LUCIO; NIEBLING, STEPHAN; CUSTÓDIO, TÂNIA F. ; LOEW, CHRISTIAN; SCHWARZ, JENNIFER J.; REMANS, KIM; CRAIG, PATRICIO O. ; OTERO, LISANDRO H.; KLINKE, SEBASTIÁN; GARCÍA-ALAI, MARÍA; SANCHEZ, IGNACIO E.; ALONSO, LEONARDO G.

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Bethesda, Maryland; Año: 2021 vol. 297 p. 101175 - 101188

0021-9258

The spike protein isthe main protein component of the SARS-CoV-2 virion surface. Thespike receptor-binding motif mediates recognition of the humanangiotensin-converting enzyme 2 (hACE2) receptor, a critical step ininfection, and is the preferential target for spike-neutralizingantibodies. Post-translational modifications of the spikereceptor-binding motif have been shown to modulate viral infectivityand host immune response, but these modifications are still beingexplored. Here we studied asparagine deamidation of the spikeprotein, a spontaneous event that leads to the appearance of asparticand isoaspartic residues, which affect both the protein backbone andits charge. We used computational prediction and biochemicalexperiments to identify five deamidation hotspots in the SARS-CoV-2spike protein. Asparagine residues 481 and 501 in thereceptor-binding motif deamidate with a half-life of 16.5 and 123days at 37°C, respectively. Deamidation is significantly slowed at4°C, indicating a strong dependence of spike protein molecular agingon environmental conditions. Deamidation of the spikereceptor-binding motif decreases the equilibrium constant for bindingto the hACE2 receptor more than 3.5-fold, yet its high conservationpattern suggests some positive effect on viral fitness. We propose amodel for deamidation of the full SARS-CoV-2 virion illustrating howdeamidation of the spike receptor-binding motif could lead to theaccumulation on the virion surface of a non-negligible chemicallydiverse spike population in a timescale of days. Our findings providea potential mechanism for molecular aging of the spike protein withsignificant consequences for understanding virus infectivity andvaccine development.p { margin-bottom: 0.25cm; line-height: 115% }