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Enhanced local symmetry interactions globally stabilize a mutant virus capsid that maintains infectivity and capsid dynamics

Academic Article
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Overview

authors

  • Speir, J. A.
  • Bothner, B.
  • Qu, C. X.
  • Willits, D. A.
  • Young, M. J.
  • Johnson Jr., John

publication date

  • April 2006

journal

  • Journal of Virology  Journal

abstract

  • Structural transitions in viral capsids play a critical role in the virus life cycle, including assembly, disassembly, and release of the packaged nucleic acid. Cowpea chlorotic mottle virus (CCMV) undergoes a well-studied reversible structural expansion in vitro in which the capsid expands by 10%. The swollen form of the particle can be completely disassembled by increasing the salt concentration to 1 M. Remarkably, a single-residue mutant of the CCMV N-terminal arm, K42R, is not susceptible to dissociation in high salt (salt-stable CCMV [SS-CCMV]) and retains 70% of wild-type infectivity. We present the combined structural and biophysical basis for the chemical stability and viability of the SS-CCMV particles. A 2.7-A resolution crystal structure of the SS-CCMV capsid shows an addition of 660 new intersubunit interactions per particle at the center of the 20 hexameric capsomeres, which are a direct result of the K42R mutation. Protease-based mapping experiments of intact particles demonstrate that both the swollen and closed forms of the wild-type and SS-CCMV particles have highly dynamic N-terminal regions, yet the SS-CCMV particles are more resistant to degradation. Thus, the increase in SS-CCMV particle stability is a result of concentrated tethering of subunits at a local symmetry interface (i.e., quasi-sixfold axes) that does not interfere with the function of other key symmetry interfaces (i.e., fivefold, twofold, quasi-threefold axes). The result is a particle that is still dynamic but insensitive to high salt due to a new series of bonds that are resistant to high ionic strength and preserve the overall particle structure.

subject areas

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Bromovirus
  • Capsid
  • Crystallography, X-Ray
  • Electrophoresis, Polyacrylamide Gel
  • Genome, Viral
  • Hydrogen Bonding
  • Hydrogen-Ion Concentration
  • Kinetics
  • Models, Molecular
  • Molecular Weight
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Secondary
  • RNA, Viral
  • Serine Endopeptidases
  • Sodium Chloride
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Trypsin
  • Water
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Identity

International Standard Serial Number (ISSN)

  • 0022-538X

Digital Object Identifier (DOI)

  • 10.1128/jvi.80.7.3582-3591.2006

PubMed ID

  • 16537626
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Additional Document Info

start page

  • 3582

end page

  • 3591

volume

  • 80

issue

  • 7

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