 After the cleavage F0 precursor yields two disulfide-linked subunits F1 and F2.Paramyxoviruses use different host cell proteases to activate their F-proteins.Sendai virus uses activating proteases that are serine endopeptidases represented by tryptase beta 2-(TPSB2),WikiGenes - Collaborative Publishing (which has aliases such as tryptase II, tryptase Clara, club cells tryptase, mast cells tryptase,) trypsin 1 (PRSS1), mini-plasmin (PLG) and transmembrane serine protease 2 (TMPRSS2).