283548 Directed Evolution of Influenza Hemagglutinin (HA) Reveals Novel pH-Sensing Mutants

Wednesday, October 31, 2012: 2:00 PM
Westmoreland West (Westin )
J. Vincent Price, Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, Jeong H. Lee, Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, Morgan R. Baltz, Chemical and Biomolecular Engineering, University of Tennessee and Eric T. Boder, Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN

Hemagglutinin (HA) is a viral fusion protein that undergoes an irreversible conformational change upon acidification to catalyze the fusion of endosomal and viral membranes.  Given the ubiquity of membrane fusion processes in nature, engineering a fusion protein for use in a drug or gene delivery vesicle, possibly promoting liposome fusion, would be a worthwhile endeavor.  We have employed directed evolution to identify novel mutants with activation pH across a range of 4.8 – 6.0; wild-type HA activates around pH 5.2. On the surface of transduced cells, a small number of engineered HA with altered pH sensing phenotypes can trigger activation of an excess of wild-type HA (or vice versa) by an autocatalytic mechanism, suggesting the ability to develop modular protein-based materials with separately tuned sensing and effector modules. Examination of library mutants has enabled us to identify individual amino acids responsible for phenotypic changes and thus provides additional structure-function insight.

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