Figure 4.

In vitro enzymatic assay of Kex2p activity. Equal amounts of membranes prepared from indicated strains were assayed for Kex2p activity and Western blot (inset). Activity was measured as the fluorescence released by cleavage of pERTKR-MCA at 25°C in the presence 1 mM CaCl₂ or 10 mM EDTA and expressed in fluorescence units per hour (F.U./h). Values are the mean of duplicates. Immunoblots were quantified by digital scanning and expressed in arbitrary units (1 for KEX2HA, 1.92 for Δprokex2HA, and 0.67 for Δprokex2HA + preprokex2).