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Journal of Virology, September 2000, p. 8048-8052, Vol. 74, No. 17
Department of Virology, Swedish Institute for
Infectious Disease Control, Karolinska Institute, 171 82 Solna,
Sweden
Received 15 February 2000/Accepted 8 June 2000
Rotavirus is one of very few viruses that utilize the endoplasmic
reticulum (ER) for assembly, and therefore it has been used as an
attractive model to study ER-associated protein folding. In this study,
we have examined the requirements for metabolic energy (ATP) for
correct folding of the luminal and ER-associated VP7 of rotavirus. We
found that VP7 rapidly misfolds in an energy-depleted milieu and is not
degraded within 60 min. We also found that VP7 attained a stable
minimum-energy state soon after translation in the ER. Most
surprisingly, energy-misfolded VP7 could be recovered and establish
correct disulfide bonds and antigenicity following a shift to an
ATP-rich milieu. Using a Semliki Forest virus expression system, we
observed that VP7 requires ATP and cellular, but not viral, factors for
correct disulfide bond formation. Our results show for the first time
that the disulfide bond formation of rotavirus VP7 is an ATP-dependent
process. It has previously been shown that chaperones hydrolyze ATP
during interaction with newly synthesized polypeptides and prevent
nonproductive intra- and intermolecular interactions. The most
reasonable explanation for the energy requirement of VP7 is thus a
close interaction during folding with an ATP-dependent chaperone, such
as BiP (Grp78), and possibly with protein disulfide isomerase. Taken
together, our observations provide new information about folding of
ER-associated proteins in general and rotavirus VP7 in particular.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
ATP Is Required for Correct Folding and Disulfide
Bond Formation of Rotavirus VP7
*
Corresponding author. Mailing address: Department of
Virology, Swedish Institute for Infectious Disease Control, Karolinska Institute, 171 82 Solna, Sweden. Phone: 46-8-4572696. Fax: 46-8-301635. E-mail: Lensve{at}mbox.ki.se.
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