Charged N-terminus of Influenza Fusion Peptide Facilitates Membrane Fusion.

Remigiusz Worch,Joanna Krupa,Anita Dudek,Anna Szymaniec,Piotr Setny

doi:10.3390/ijms19020578

Abstract

Cleavage of hemagglutinin precursor (HA0) by cellular proteases results in the formation of two subunits, HA1 and HA2. The N-terminal fragment of HA2, named a fusion peptide (HAfp), possess a charged, amine N-terminus. It has been shown that the N-terminus of HAfp stabilizes the structure of a helical hairpin observed for a 23-amino acid long peptide (HAfp1-23), whose larger activity than HAfp1-20 has been demonstrated recently. In this paper, we analyze the effect of N-terminal charge on peptide-mediated fusion efficiency and conformation changes at the membrane interface by comparison with the corresponding N-acetylated peptides of 20- and 23-amino acid lengths. We found that higher fusogenic activities of peptides with unmodified amino termini correlates with their ability to form helical hairpin structures oriented perpendicularly to the membrane plane. Molecular dynamics simulations showed that acetylated peptides adopt open and surface-bound conformation more often, which induced less disorder of the phospholipid chains, as compared to species with unmodified amino termini.

Highlights

Influenza virus hemagglutinin is a trimeric, single-span transmembrane protein and is solely involved in membrane fusion between the viral envelope and the endosomal membrane of the infected host cell
This issue indicated that the length of a fusion peptide, possibly warranting its ability to reach the active conformation, may be an important factor to consider in the studies devoted to the mechanism of membrane fusion
We performed lipid mixing assay on large unilamellar vesicles (LUVs) based on NBD-rhodamine fluorescence energy transfer (FRET)

Summary

Introduction

Influenza virus hemagglutinin is a trimeric, single-span transmembrane protein and is solely involved in membrane fusion between the viral envelope and the endosomal membrane of the infected host cell It is composed of two subunits, HA1 and HA2, which are created by the proteolytic cleavage of hemagglutinin precursor HA0. In the same seminal paper, the authors showed that HAfp was able to induce membrane fusion, in contrast to HAfp which appeared to be a poor fusogenic agent, even at concentrations saturating binding to POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) vesicles This issue indicated that the length of a fusion peptide, possibly warranting its ability to reach the active conformation, may be an important factor to consider in the studies devoted to the mechanism of membrane fusion. In agreement with the above observations, in our recent paper, we showed that the presence of the three C-terminal W21-Y22-G23 residues promotes the formation of a helical hairpin, which orients itself perpendicularly to the membrane plane and induces more disorder in the surrounding lipids than the less structured HAfp1-20 [11]

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Discussion

Conclusion