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Journal of Virology, April 1999, p. 3054-3061, Vol. 73, No. 4
Department of Microbiology, School of
Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania,1 and Department of
Pathology, Harvard Medical School, Boston,
Massachusetts2
Received 3 September 1998/Accepted 23 December 1998
The receptor for the subgroup A avian sarcoma and leukosis viruses
[ASLV(A)] is the cellular glycoprotein Tva. A soluble form of Tva,
sTva, was produced and purified with a baculovirus expression system.
Using this system, 7 to 10 mg of purified sTva per liter of cultured
Sf9 cells was obtained. Characterization of the carbohydrate modification of sTva revealed that the three N glycosylation sites in
sTva were differentially utilized; however, the O glycosylation common
to Tva produced in mammalian and avian cells was not observed. Purified
sTva demonstrates significant biological activity, specifically blocking infection of avian cells by ASLV(A) with a 90% inhibitory concentration of ~25 pM. A quantitative enzyme-linked immunosorbent assay, developed to assess the binding of sTva to ASLV envelope glycoprotein, demonstrates that sTva has a high affinity for EnvA, with
an apparent dissociation constant of approximately 0.3 nM. Once they
are bound, a very stable complex is formed between EnvA and sTva, with
an estimated complex half-life of 6 h. The soluble receptor
protein described here represents a valuable tool for analysis of the
receptor-envelope glycoprotein interaction and for structural analysis
of Tva.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Production and Characterization of a Soluble, Active Form of
Tva, the Subgroup A Avian Sarcoma and Leukosis Virus
Receptor
*
Corresponding author. Mailing address: Department of
Microbiology, University of Pennsylvania School of Medicine, 225 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104-6076. Phone: (215) 573-3509. Fax: (215) 573-4184. E-mail:
pbates{at}mail.med.upenn.edu.
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