Overlapping and independent structural roles for human papillomavirus type 16 L2 conserved cysteines

Virology. 2009 Oct 25;393(2):295-303. doi: 10.1016/j.virol.2009.08.010. Epub 2009 Sep 5.

Abstract

Cryoelectron microscopy images of HPV16 pseudovirions (PsV) depict that each pentamer of L1 can be occluded with a monomer of L2. Further research suggests that an N-terminal external loop of L2 exists, which is the target of neutralizing and cross-neutralizing antibodies. Here we show that N-terminal L2 cysteine residues, Cys22 and Cys28, have overlapping and independent structural roles, which affect both early- and late-stage assembly events. Substitution of either cysteine residue enhances infectivity markedly in comparison to wild-type HPV16. However, only Cys22Ser 20-day virions become nearly as stable as wild type. In addition, Cys22Ser, and Cys22,28Ser 20-day virions have lost their susceptibility to neutralization by anti-L2 antibodies, whereas Cys28Ser 20-day virions remain partially susceptible. These results suggest that Cys28 is necessary for late-stage stabilization of capsids, while Cys22 is necessary for proper display of L2 neutralizing epitopes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Capsid Proteins / genetics*
  • Cell Line
  • Cysteine / genetics*
  • Human papillomavirus 16 / genetics
  • Human papillomavirus 16 / pathogenicity*
  • Humans
  • Keratinocytes / virology
  • Mutagenesis, Site-Directed
  • Neutralization Tests
  • Oncogene Proteins, Viral / genetics*
  • Papillomavirus Infections / genetics
  • Virion / genetics
  • Virion / pathogenicity

Substances

  • Capsid Proteins
  • L2 protein, Human papillomavirus type 16
  • Oncogene Proteins, Viral
  • Cysteine