# Biophysical studies of viral membrane fusion proteins

> **NIH NIH R01** · UNIV OF MASSACHUSETTS MED SCH WORCESTER · 2022 · $502,500

## Abstract

SUMMARY
Influenza A virus (IAV) hemagglutinin (HA) is the canonical example of a class-I viral fusion protein, and thus
provides an ideal model system for understanding the fusion mechanisms of many different viruses. Numerous
other viral envelope glycoproteins, including the SARS-CoV-2 spike, are believed to mediate fusion by a
comparable mechanism. Our long-term goal is to establish a complete mechanistic framework of class-I viral
fusion. We further aim to identify conserved and divergent features of the fusion mechanisms of distinct viruses,
generating specific models that fit within the general framework. HA resides on the surface of the IAV virion and
facilitates attachment to the target cell surface through the receptor-binding domain (HA1) engaging SA moieties.
Following endocytosis and trafficking to the late endosome, HA promotes fusion of the viral and endosomal
membranes. The model of HA-mediated membrane fusion describes a “spring-loaded” metastable prefusion
conformation at neutral pH. Dissociation of HA1 from the fusion domain (HA2) allows HA2 to undergo a cascade
of conformational changes that drive membrane fusion. While extensive structural data exist for HA pre- and
postfusion, and alternative conformations have been visualized and inferred, the conformational trajectory that
leads to membrane fusion, including the adoption of anticipated intermediates, has never been explicitly
validated. Nor has the order and timing of conformational changes and membrane fusion been determined. Here,
we will utilize a multifaceted approach involving single-molecule Förster resonance energy transfer imaging,
single-virion fusion, cryoelectron tomography, and molecular dynamic simulation to directly visualize the
conformational trajectory undergone by HA during membrane fusion. We will explore the roles of virion
morphology, HA density and cooperativity, and target membrane lipid content in mediating HA conformational
changes and the mechanism of fusion. We will describe the allosteric connection between distal regions of HA
that regulate the timing of fusion, drawing comparison to SARS-CoV-2 S. Finally, we will biophysically
characterize the phenotypic differences between human and avian IAV strains to determine what prevents avian
IAV strains from entering the human population.

## Key facts

- **NIH application ID:** 10466013
- **Project number:** 1R01GM143773-01A1
- **Recipient organization:** UNIV OF MASSACHUSETTS MED SCH WORCESTER
- **Principal Investigator:** James B Munro
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $502,500
- **Award type:** 1
- **Project period:** 2022-07-01 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10466013

## Citation

> US National Institutes of Health, RePORTER application 10466013, Biophysical studies of viral membrane fusion proteins (1R01GM143773-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10466013. Licensed CC0.

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