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J. Virol., 01 1998, 133-141, Vol 72, No. 1
B Schroth-Diez, E Ponimaskin, H Reverey, MF Schmidt and A Herrmann
The role of the sequence of transmembrane and cytoplasmic/intraviral
domains of influenza virus hemagglutinin (HA, subtype H7) for HA- mediated
membrane fusion was explored. To analyze the influence of the two domains
on the fusogenic properties of HA, we designed HA-chimeras in which the
cytoplasmic tail and/or transmembrane domain of HA was replaced with the
corresponding domains of the fusogenic glycoprotein F of Sendai virus.
These chimeras, as well as constructs of HA in which the cytoplasmic tail
was replaced by peptides of human neurofibromin type 1 (NF1) or c-Raf-1,
NF78 (residues 1441 to 1518), and Raf81 (residues 51 to 131), respectively,
were expressed in CV-1 cells by using the vaccinia virus-T7 polymerase
transient-expression system. Wild-type and chimeric HA were cleaved
properly into two subunits and expressed as trimers. Membrane fusion
between CV-1 cells and bound human erythrocytes (RBCs) mediated by parental
or chimeric HA proteins was studied by a lipid-mixing assay with the
lipid-like fluorophore octadecyl rhodamine B chloride (R18). No profound
differences in either extent or kinetics could be observed. After the pH
was lowered, the above proteins also induced a flow of the aqueous
fluorophore calcein from preloaded RBCs into the cytoplasm of the
protein-expressing CV-1 cells, indicating that membrane fusion involves
both leaflets of the lipid bilayers and leads to formation of an aqueous
fusion pore. We conclude that neither HA-specific sequences in the
transmembrane and cytoplasmic domains nor their length is crucial for
HA-induced membrane fusion activity.
Copyright © 1998, American Society for Microbiology
Fusion activity of transmembrane and cytoplasmic domain chimeras of the influenza virus glycoprotein hemagglutinin
Institut fur Biologie/Biophysik, Mathematisch-Naturwissenschaftliche Fakultat I, Humboldt-Universitat zu Berlin, Germany.
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