In vitro papillomavirus capsid assembly analyzed by light scattering

• Published in: Virology (New York, N.Y.) Vol. 325; no. 2; pp. 320 - 327
• Main Authors: Casini, Greg L., Graham, David, Heine, David, Garcea, Robert L., Wu, David T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-08-2004
• Subjects: Capsid - physiology; Capsid - ultrastructure; Capsid formation kinetics; Capsid Proteins; Human papillomavirus 11; Kinetics; Light; Light scattering; Microscopy, Electron; Oncogene Proteins, Viral - chemistry; Oncogene Proteins, Viral - genetics; Oncogene Proteins, Viral - physiology; Papillomaviridae - genetics; Papillomaviridae - physiology; Papillomaviridae - ultrastructure; Protein nucleation; Protein polymerization; Protein Structure, Quaternary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Scattering, Radiation; Virus assembly; Virus Assembly - physiology; Capsid formation kinetics; Virus assembly; Protein nucleation; Light scattering; Protein polymerization
• DOI: 10.1016/j.virol.2004.04.034
• EISSN: 1096-0341
• ISSN: 0042-6822

Pentamers of the L1 major capsid protein of human papillomavirus (HPV type 11) were purified after expression in
E. coli and analyzed for the kinetics of in vitro capsid self-assembly using multi-angle light scattering (MALS). Pentamers self-assembled into capsid-like structures at a rate that was a function of protein concentration. The kinetics of capsid formation were sigmoidal with a concentration-dependent lag phase, followed by a rapid increase in polymerization. Nucleation size and the rate order of subsequent subunit addition were calculated from the concentration dependence of the extent of capsid formation and the rate of the fast phase, respectively. Assembly was second order with a nucleation size of two pentamers. Thus, we suggest that dimers of pentamers are the nucleus for L1 assembly into capsid-like structures, with rapid sequential addition of single pentamers to the growing shell. Although studied in vitro without accessory factors that may be present in vivo, these data are in contrast with the “five-around-one” assembly nucleus previously proposed for polyomaviruses.