Analysis of the Cytoplasmic Tail Domain of Hendra Virus Fusion Protein

Abstract

Hendra virus (HeV), a recently emerged paramyxovirus, produces two glycoproteins: a fusion (F) protein and an attachment protein, which together mediate virus-cell fusion and cell-cell fusion. The F protein is produced in a precursor form, F0, which must be proteolytically cleaved into the disulfide-linked F1 and F2 heterodimer by the endosomal protease cathepsin L to be fusogenically active. The Hendra F protein also contains four N-linked carbohydrate additions, two of which have been shown to affect protein folding and membrane fusion. The F1 portion of the fusion protein has a number of important domains, including a fusion peptide, two heptad repeat regions, a transmembrane domain and 28 amino acid cytoplasmic tail domain. While mutations in the cytoplasmic tail regions have been studied for a number of paramyxovirus F proteins, the role of this domain in folding, processing and membrane fusion is still unclear. We have created a series of deletion mutants along the cytoplasmic tail domain of the Hendra F protein, resulting in proteins with cytoplasmic tails of varying length. All of the deletion mutants were expressed in transient cell culture expression system. However, heterogeneity in size was observed for a number of mutants, and this could be resolved by removal of the N-linked carbohydrates, suggesting that the cytoplasmic tail can affect branching of the N-linked carbohydrates. In addition, alterations in fusion properties were observed for some of the mutants, indicating that this cytoplasmic domain also plays a role in membrane fusion promotion of this important viral protein. Funded by grants from NIH.