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. 2020 Jun 5;11:2841. doi: 10.1038/s41467-020-16639-1

Fig. 1. Schematic presentation and negative-staining transmission electron microscopy (TEM) of assembly-deficient HPV L1 pentamers and their capsomere-hybrid assembly via the formation of single inter-disulfide bonds.

Fig. 1

Scale bar, 100 nm. The replacement of Cys175 or Cys428 of HPV L1 with Ala impedes self-assembly into VLPs; albeit, folding to capsomere-characteristic donut-like pentamers is retained, as shown in the TEM views. Left/top panel: mutants of HPV6, HPV16, and HPV52 L1-C175A/C428A were de-thiolated on aa175/aa428 but preserve the thiol group on aa428/aa175, which abrogate their self-assembly into VLPs with respect to the WT HPV L1. a–i Right lower panel: combination of any C175 mutant and any C428 mutant (homologous type or heterologous type of HPV), allows chVLP assembly of two single-point mutated pentamers with reciprocal disulfide bonding potentials. Schematic cartoon (left top region) illustrates the reciprocal linkage of Cys175 and Cys428 from pentamer mutants C428A and C175A, respectively, for chVLP assembly. Also refer to Supplementary Figs. 1 and 9. One representative image from three biological repeats is shown.