Lipid-anchored influenza hemagglutinin promotes hemifusion, not complete fusion

George W. Kemble*, Tsafi Danieli, Judith M. White

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

453 Scopus citations


It has been proposed that membrane fusion events such as virus-cell fusion proceed through a hemifusion intermediate, a state where lipids but not contents of the fusing compartments mix. We engineered the influenza hemagglutinin (HA) such that it would be anchored in membranes via a glycosylphosphatidylinositol (GPI) tail. GPI-anchored HA forms a trimer that can bind red blood cells (RBCs) and change conformation under fusion-inducing conditions. Using RBCs labeled with fluorescent lipid or fluorescent soluble content probes, we found that GPI-anchored HA mediated lipid mixing with similar time course and efficiency as wt-HA, yet did not mediate transfer of soluble contents. Hence, GPI-anchored HA appears to initiate, but not complete, a fusion reaction. We interpret our results as evidence for uncoupling a physiological fusion reaction, for trapping a hemifusion intermediate, and for assigning a role to a transmembrane domain in a fusion event.

Original languageAmerican English
Pages (from-to)383-391
Number of pages9
Issue number2
StatePublished - 28 Jan 1994
Externally publishedYes

Bibliographical note

Funding Information:
Address correspondence to J. M. W. We are very grateful to E. Almeida for help with confocal microscopy and to P. Straight for excellent technical assistance. We also thank J. Skehel for the anti-HA monoclonal antibody, Y. Henis for helpful discussions, H. Czerwonka for manuscript preparation, and S. Green and members of the White lab for critical reading of the manuscript. The work was supported by a grant from the National Institutes of Health (Al22470) to J. M. W.; G. K. was supported by a fellowship from the Universitywide Taskforce on AIDS.


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