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J. Virol., 10 1995, 5995-6004, Vol 69, No. 10
JN Reitter, T Sergel and TG Morrison
The paramyxovirus fusion proteins have a highly conserved leucine zipper
motif immediately upstream from the transmembrane domain of the F1 subunit
(R. Buckland and F. Wild, Nature [London] 338:547, 1989). To determine the
role of the conserved leucines in the oligomeric structure and biological
activity of the Newcastle disease virus (NDV) fusion protein, the heptadic
leucines at amino acids 481, 488, and 495 were changed individually and in
combination to an alanine residue. While single amino acid changes had
little effect on fusion, substitution of two or three leucine residues
abolished the fusogenic activity of the protein, although cell surface
expression of the mutants was higher than that of the wild-type protein.
Substitution of all three leucine residues with alanine did not alter the
size of the fusion protein oligomer as determined by sedimentation in
sucrose gradients. Furthermore, deletion of the C-terminal 91 amino acids,
including the leucine zipper motif and transmembrane domain, resulted in
secretion of an oligomeric polypeptide. These results indicate that the
conserved leucines are not necessary for oligomer formation but are
required for the fusogenic ability of the protein. When the polar face of
the potential alpha helix was altered by nonconservative changes of serine
to alanine (position 473), glutamic acid to lysine or alanine (position
482), asparagine to lysine (position 485), or aspartic acid to alanine
(position 489), the fusogenic ability of the protein was not significantly
disrupted. In addition, a double mutant (E482A,D489A) which removed
negative charges along one side of the helix had negligible effects on
fusion activity.
Copyright © 1995, American Society for Microbiology
Mutational analysis of the leucine zipper motif in the Newcastle disease virus fusion protein
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655, USA.
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