Human parainfluenza virus 3 fusion glycoprotein (HPIV3 F protein)

The **Human parainfluenza virus 3 fusion glycoprotein (HPIV3 F protein)** is a trimeric viral envelope glycoprotein classified as a class I fusion protein that mediates the critical step of membrane fusion between the virion and host cell, enabling viral entry and infection[5][6][7]. The F protein is initially synthesized as an inactive precursor (F0), which is cleaved by host cell proteases (e.g., TMPRSS2 and TMPRSS13) into the active form necessary for membrane fusion[9]. Structurally, it transitions from a metastable prefusion state to a highly stable postfusion state, with significant conformational rearrangements, including formation of a central coiled coil and six-helix bundle in the postfusion trimer[2][3][4]. The F protein functions in concert with the hemagglutinin-neuraminidase (HN) protein, which binds sialic acid-containing receptors on the host cell and triggers F activation upon receptor engagement[5][7]. HPIV3 F is a validated therapeutic target for both antibody-based therapies and small-molecule fusion inhibitors, and is a leading antigenic candidate for HPIV3 vaccine development due to its essential role in viral entry and its prominent surface exposure on the virion[8].

Other names

HPIV3 FHPIV3 fusion proteinParainfluenza virus 3 fusion glycoproteinFusion (F) glycoprotein

Neutralizing antibodies (such as PIA174) stabilize the prefusion conformation of F, preventing the conformational changes necessary for membrane fusion and viral entry[7][8] Fusion inhibitors may block conformational changes or peptide-mediated membrane insertion.