Differences in Oligomerization of the SARS-CoV-2 Envelope Protein, Poliovirus VP4, and HIV Vpu

Figure 1.. Workflow illustrating the process of studying the oligomeric states of viroporins in various detergents. Electrospray ionization (A) is performed on the protein in detergent, yielding a raw mass spectrum of the sample (B), which is deconvolved into a zero-charge mass spectrum (C). The resulting peak intensities for different oligomers across different proteins and detergent conditions are averaged and displayed on a grid plot (D).

Figure 2.. Representative raw mass spectra of the E protein solubilized in LDAO detergent (0.05%) at the concentration of ammonium acetate varied in each sample (0.2 – 1 M ammonium acetate). Charge states for the dimer are marked with a green diamond. Other peaks are from residual detergent bound to the dimer.

Figure 3.. Representative native raw mass spectra of VP4 that has been buffer exchanged into solutions containing 0.2 M ammonium acetate and C8E4 detergent that are pH 5, 7, and 9. The deconvolved mass spectra are inset. Monomer peaks are marked with a green circle.

Figure 4.. Representative native raw mass spectra of Vpu solubilized in 0.2 M ammonium acetate with (A) C8E4, (B) Triton X-100, and (C) LDAO detergents. The deconvolved spectra of each condition are inset, and oligomeric states are annotated with shapes.

Figure 5.. Grid showing the average oligomeric state intensities, ranging from monomer through hexamer, of viroporins M2, Vpu, E Protein, and VP4 in different types of detergent. The darker the color shown, the higher the intensity of the signal for that oligomer.