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Originally published In Press as doi:10.1074/jbc.M010037200 on November 22, 2000
J. Biol. Chem., Vol. 276, Issue 10, 7415-7421, March 9, 2001
The Metastable State of Nucleocapsids of Enveloped Viruses as
Probed by High Hydrostatic Pressure*
Luciane P.
Gaspar ,
Alexandre F.
Terezan §,
Anderson S.
Pinheiro ,
Débora
Foguel ,
Moacyr A.
Rebello¶, and
Jerson L.
Silva
From the Programa de Biologia Estrutural,
Departamento de Bioquímica Médica, Instituto de
Ciências Biomédicas, Centro Nacional de Ressonância
Magnética Nuclear de Macromoléculas and ¶ Departamento
de Virologia, Instituto de Microbiologia Professor Paulo Góes,
Universidade Federal do Rio de Janeiro,
21941-590, RJ, Brazil
Enveloped viruses fuse their membranes with
cellular membranes to transfer their genomes into cells at the
beginning of infection. What is not clear, however, is the role of the
envelope (lipid bilayer and glycoproteins) in the stability of the
viral particle. To address this question, we compared the stability
between enveloped and nucleocapsid particles of the
alphavirus Mayaro using hydrostatic pressure and
urea. The effects were monitored by intrinsic fluorescence, light
scattering, and binding of fluorescent dyes, including
bis(8-anilinonaphthalene-1-sulfonate) and ethidium bromide. Pressure
caused a drastic dissociation of the nucleocapsids as determined by
tryptophan fluorescence, light scattering, and gel filtration
chromatography. Pressure-induced dissociation of the nucleocapsids was
poorly reversible. In contrast, when the envelope was present, pressure
effects were much less marked and were highly reversible. Binding of
ethidium bromide occurred when nucleocapsids were dissociated under
pressure, indicating exposure of the nucleic acid, whereas enveloped
particles underwent no changes. Overall, our results demonstrate
that removal of the envelope with the glycoproteins leads the particle
to a metastable state and, during infection, may serve as the trigger
for disassembly and delivery of the genome. The envelope acts as a
"Trojan horse," gaining entry into the host cell to allow
release of a metastable nucleocapsid prone to disassembly.
*
This work was supported in part by an international grant
from the Howard Hughes Medical Institute (to J. L. S.) and by grants from Fundação de Amparo a Pesquisa do Estado do Rio de
Janeiro (FAPERJ), Conselho Nacional de Desenvolvimento
Científico (PADCT and Pronex programs), and Financiadora de
Estudos e Projetos (FINEP) of Brazil (to J. L. S.).The costs of publication of this
article were defrayed in part by the
payment of page charges. The article must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
§
Recipient of a fellowship from Scientific Instruments Co. do Brazil.
A Howard Hughes Medical Institute International Researcher. To
whom correspondence should be addressed. Tel.: 55-21-590-4548; Fax:
55-21-270-8647. E-mail: jerson@bioqmed.ufrj.br.
Copyright © 2001 by The American Society for Biochemistry and Molecular Biology, Inc.

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