Expression of CPY in several strains of yeast. (a) Protease activity as measured by hydrolysis of using N-acetyl-dl-phenylalanine p-nitrophenyl ester, a synthetic substrate for CPY. The solid bars represent protease activity under nonstress conditions, and the gray bars represent activity in the presence of 2 mM DTT. (b) Western blots of CPY expression. The unprocessed and inactive, 69-kDa proenzyme band is labeled p1CPY, and the active, mature, 61-kDa band is labeled mCPY.