Overlapping and independent structural roles for human papillomavirus type 16 L2 conserved cysteines.
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.
Conway
Michael J
MJ
Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
Alam
Samina
S
Christensen
Neil D
ND
Meyers
Craig
C
D019943:Amino Acid Substitution; D036022:Capsid Proteins / Q000235:genetics*; D002460:Cell Line; D003545:Cysteine / Q000235:genetics*; D052162:Human papillomavirus 16 / Q000235:genetics / Q000472:pathogenicity*; D006801:Humans; D015603:Keratinocytes / Q000821:virology; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D030361:Papillomavirus Infections / Q000235:genetics; D014771:Virion / Q000235:genetics / Q000472:pathogenicity
D036022:Capsid Proteins; C063316:L2 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D003545:Cysteine