Poster abstracts

Poster number 106 submitted by Stephanie Hicks

The apical loop of the f2 peptide in the respiratory syncytial virus fusion protein plays an essential role in membrane fusion.

Stephanie N. Hicks (OSBP), Supranee Chaiwatpongsakorn (The Research Institute at Nationwide Childrens Hospital Vaccines and Immunity), Mark Peeples (The Research Institute at Nationwide Childrens Hospital Vaccines and Immunity)

Abstract:
The respiratory syncytial virus (RSV) fusion (F) protein is a trimeric, membrane anchored glycoprotein that mediates fusion of the viral envelope membrane and target cell membrane to initiate infection. The F protein is initially expressed in its active, metastable, and high energy prefusion conformation . To mediate fusion, the F protein triggers, embeds the fusion peptide into a target cell membrane, and refolds to the 6 helix-bundle postfusion conformation, bringing the viral and cellular membranes together. Fusion is accomplished without help from the RSV attachment protein. The interaction that causes the F protein to trigger is not known. We examined 12 residues at the apex of the RSV F protein by alanine scanning mutagenesis in a cell-cell fusion assay for their importance in RSV fusion. Six of these residues were essential for function: I64, K65, K66, K68, D73, and K75. The non-polar I64 appears to be required for initial protein folding rather than its function. The remaining 5 residues are charged, polar amino acids, whose specific charge are required for function, except for D73 where an uncharged residue did not affect fusion. K65, K66, and K68 are grouped along the side of the protein apex and mutations to these residues appear to hinder protein refolding following a forced, unnatural triggering event. D73 and K75 are located at the apex of the protein, lining the apical pore formed by the trimer. Mutation at either site does not hinder fusion following forced triggering. These residues, particularly K75, are likely directly involved in triggering the prefusion F protein.

Keywords: RSV, Fusion