INTERACTION OF CYSTEINE PROTEINASES WITH RECOMBINANT KININOGEN DOMAIN-2, EXPRESSED IN ESCHERICHIA-COLI

The calpain-binding domain 2 of the kininogens, the major plasma inhib itors of cysteine proteinases, was expressed in Escherichia coli. Expr ession of soluble protein was optimal at 15 degrees C and was augmente d by growing the bacteria in sorbitol and betaine. The recombinant dom ain showed high affinity (K-i 0.3-1 nM) for cathepsin L and papain, an d a somewhat lower affinity (K-i similar to 15 nM) for calpain. The bi nding to cathepsin B was substantially weaker, and no inhibition of ac tinidin and cathepsin B was detected, The affinity for cathepsin L was comparable to that reported for the domain isolated from plasma L-Kin inogen, whereas the affinities for papain and calpain were about tenfo ld lower. The latter difference may be due to the recombinant domain b eing nonglycosylated.