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J. Virol., 03 1995, 1435-1443, Vol 69, No. 3
BL Fredericksen and MA Whitt
We have introduced amino acid substitutions into two regions of the
extracellular domain of the vesicular stomatitis virus (VSV) glycoprotein
(G protein) and examined the effect of these mutations on protein
transport, low-pH-induced stability of G protein oligomers, and membrane
fusion activity. We suggested previously that the region between amino
acids 118 and 139 may be important for the membrane fusion activity of G
protein, on the basis of the characterization of a fusion-defective G
protein mutant (M. A. Whitt, P. Zagouras, B. Crise, and J. K. Rose, J.
Virol. 64:4907-4913, 1990). It has also been postulated by others that this
region as well as the region between amino acids 181 and 212 may constitute
putative internal fusion domains of VSV G protein. In this report, we show
that three different amino acids substitutions between residues 118 and 139
(G-124-->E, P-127-->D, and A-133-->K) either altered or abolished
low-pH-dependent membrane fusion activity. In contrast, substitutions
between residues 192 and 212 resulted either in G proteins that had
wild-type fusion activity or in mutant proteins in which the mutation
prevented transport of G protein to the cell surface. Two of the
substitutions between residues 118 and 139 (G-124-->E and P-127-->D)
resulted in G proteins that were fusion defective at pH 5.7, although
syncytia were observed after cells were treated with fusion buffer at pH
5.5, albeit at levels significantly less than that induced by wild-type G
protein. Interestingly, when either G-124-->E or P-127-->D was
incorporated into tsO45 virions, the resulting particles were not
infectious, presumably because the viral envelope was not able to fuse with
the proper intracellular membrane. These results support the hypothesis
that the region between amino acids 118 and 139 is important for the
membrane fusion activity of VSV G protein and may constitute an internal
fusion domain.
Copyright © 1995, American Society for Microbiology
Vesicular stomatitis virus glycoprotein mutations that affect membrane fusion activity and abolish virus infectivity
Department of Microbiology and Immunology, University of Tennessee, Memphis 38163.
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