Abstract
Nonequivalent bonding of identical protein subunits occurs in the polyomavirus capsid where identical pentameric capsomeres occupy both hexavalent and pentavalent positions in the icosahedral surface lattice1. The polyomavirus major capsid protein VP1, purified after expression of the recombinant gene in Escherichia coli2, has been isolated as capsomeres that self-assemble into capsid-like structures in vitro3. The ability to switch bonding specificity in different symmetry environments therefore must be intrinsic to the VP1 molecule. In vitro self-assembly provides an assay for VP1 mutations affecting capsomere and capsid formation. We report here that a directed mutation in the VP1 expression vector, leading to a protein truncated at the carboxy terminus, results in a mutant VP1 that forms capsomeres, but not capsids, in the in vitro assembly assay. The carboxy terminus of VP1 therefore appears to be involved in the specific bonding responsible for the non-equivalent association of capsomeres.
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Garcea, R., Salunke, D. & Caspar, D. Site-directed mutation affecting polyomavirus capsid self-assembly in vitro. Nature 329, 86–87 (1987). https://doi.org/10.1038/329086a0
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DOI: https://doi.org/10.1038/329086a0
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