.
Fusion proteins have to be produced in an inactive state in order to avoid to trigger fusion in the Golgi or other compartments upon synthesis and transport to the cell surface. Many are activated in the trans.Golgi network or at the cell surface by proteolytic cleavage which reveals the fusion peptide.
Class I
Class II
Class III
Class IV
Fusion mechanism according to the "viral fusion pore" model of Lee K:
. A different model has been described with PIV5
