Polymorphism in the assembly of polyomavirus capsid protein VP1

Polyomavirus major capsid protein VP1, purified after expression of the recombinant gene in Escherichia coli, forms stable pentamers in low-ionic strength, neutral, or alkaline solutions. Electron microscopy showed that the pentamers, which correspond to viral capsomeres, can be self-assembled into...

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Bibliographic Details
Published in:Biophysical journal 1989-11, Vol.56 (5), p.887-900
Main Authors: Salunke, D.M., Caspar, D.L., Garcea, R.L.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Capsid - genetics
Capsid - ultrastructure
Capsid Proteins
Escherichia coli - genetics
Fundamental and applied biological sciences. Psychology
General aspects
Genes, Viral
Microbiology
Microscopy, Electron
Models, Molecular
Polymorphism, Genetic
Polyomavirus - genetics
Recombinant Proteins - ultrastructure
Viral Structural Proteins - genetics
Virology
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Summary:Polyomavirus major capsid protein VP1, purified after expression of the recombinant gene in Escherichia coli, forms stable pentamers in low-ionic strength, neutral, or alkaline solutions. Electron microscopy showed that the pentamers, which correspond to viral capsomeres, can be self-assembled into a variety of polymorphic aggregates by lowering the pH, adding calcium, or raising the ionic strength. Some of the aggregates resembled the 500-A-diameter virus capsid, whereas other considerably larger or smaller capsids were also produced. The particular structures formed on transition to an environment favoring assembly depended on the pathway of the solvent changes as well as on the final conditions. Mass measurements from cryoelectron micrographs and image analysis of negatively stained specimens established that a distinctive 320-A-diameter particle consists of 24 close-packed pentamers arranged with octahedral symmetry. Comparison of this unexpected octahedral assembly with a 12-capsomere icosahedral aggregate and the 72-capsomere icosahedral virus capsid by computer graphics methods indicates that similar connections are made among trimers of pentamers in these shells of different size. The polymorphism in the assembly of VP1 pentamers can be related to the switching in bonding specificity required to build the virus capsid.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(89)82735-3