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Journal of Virology, May 2000, p. 4220-4228, Vol. 74, No. 9
Department of Biochemistry, North Carolina
State University, Raleigh, North Carolina
27695,1 and Yonsei Cancer Center,
Institute of Cancer Research, Yonsei University College of Medicine,
Seoul, Korea2
Received 18 November 1999/Accepted 7 February 2000
The envelopment of the Sindbis virus nucleocapsid in the modified
cell plasma membrane involves a highly specific interaction between the
capsid (C) protein and the endodomain of the E2 glycoprotein. We have
previously identified a domain of the Sindbis virus C protein involved
in binding to the E2 endodomain (H. Lee and D. T. Brown, Virology
202:390-400, 1994). The C-E2 binding domain resides in a hydrophobic
cleft with C Y180 and W247 on opposing sides of the cleft. Structural
modeling studies indicate that the E2 domain, which is proposed to bind
the C protein (E2 398T, 399P, and 400Y), is located at a sufficient
distance from the membrane to occupy the C protein binding cleft (S. Lee, K. E. Owen, H. K. Choi, H. Lee, G. Lu, G. Wengler,
D. T. Brown, M. G. Rossmann, and R. J. Kuhn, Structure
4:531-541, 1996). To measure the critical spanning length of the E2
endodomain which positions the TPY domain into the putative C binding
cleft, we have constructed a deletion mutant,
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
A Single Deletion in the Membrane-Proximal Region
of the Sindbis Virus Glycoprotein E2 Endodomain Blocks Virus
Assembly
K391, in which a
nonconserved lysine (E2 K391) at the membrane-cytoplasm junction of the
E2 tail has been deleted. This mutant was found to produce very low
levels of virus from BHK-21 cells due to a defect in an unidentified
step in nucleocapsid binding to the E2 endodomain. In contrast,
K391
produced wild-type levels of virus from tissue-cultured mosquito cells.
We propose that the phenotypic differences displayed by this mutant in
the two diverse host cells arise from fundamental differences in the lipid composition of the insect cell membranes which affect the physical and structural properties of membranes and thereby virus assembly. The data suggest that these viruses have evolved properties adapted specifically for assembly in the diverse hosts in which they grow.
*
Corresponding author. Mailing address: Department of
Biochemistry, North Carolina State University, Campus Box 7622, Raleigh, NC 27695-7622. Phone: (919) 515-5802. Fax: (919)
515-2047. E-mail: dennis_brown{at}ncsu.edu.
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