Parainfluenza virus fusion protein (F protein) (F protein (or F glycoprotein))

The parainfluenza virus fusion (F) protein is a class I viral fusion protein that mediates entry of paramyxoviruses into host cells by catalyzing fusion between viral and cellular membranes.[3][5] Synthesized as an inactive precursor (F0), the F protein is proteolytically cleaved by host proteases to generate the biologically active form (F1,F2), exposing a hydrophobic fusion peptide.[7] The protein exists in a metastable prefusion conformation that undergoes irreversible conformational changes upon activation by the receptor-binding protein hemagglutinin-neuraminidase (HN), leading to insertion of the fusion peptide into the target membrane and formation of a stable six-helix bundle structure.[3][4][5] This refolding process couples the energy released to the merger of viral and cellular membranes, permitting delivery of viral genetic material into the host cell.[3] The F protein is recognized as a therapeutic target for parainfluenza infections, with multiple drug development strategies in preclinical and early clinical stages, including fusion-inhibitory peptides, premature activation compounds that inactivate the virus prior to receptor engagement, and agents that block the coordinated HN-F activation process.[2][10]

Other names

Fusion glycoprotein F0 (precursor form)[12]F1,F2 (cleaved active form)[7]Class I viral fusion protein[7]Paramyxovirus F protein[3]

Premature F protein activation: Induces conformational changes in F protein to its postfusion state prior to receptor engagement, irreversibly inactivating the virus[2]. Fusion peptide sequestration: Prevents the hydrophobic fusion peptide from accessing the target bilayer by blocking conformational transitions[1]. Heptad repeat inhibition: Blocks the formation of the six-helix bundle structure required for membrane fusion[4]. HN-dependent activation prevention: Interferes with the receptor-binding protein's ability to trigger F protein conformational changes[2].