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Covalent labelling of bovine lens multicatalytic proteinase complex with [3H]di-isopropyl fluorophosphate
B J Wagner1, J W Margolis, J Yin
1Department of Biochemistry, University of Medicine and Dentistry, New Jersey Medical School, Newark.
Abstract:
Enzymatically active lens multicatalytic proteinase complex bound [3H]iPr2P-F after incubation for 3 hours at ambient temperature. Label was associated with the lowest molecular weight band (Mr 22,000) on sodium dodecyl sulfate polyacrylamide gels. This binding was inhibited by preincubation of the enzyme with the cysteine-directed reagent, p-chloromercuribenzoate, which inhibits all three hydrolytic activities of the enzyme. Leupeptin, which inhibits the arginyl-hydrolyzing component, but not the iPr2P-F-inhibitable leucyl-hydrolyzing component of the enzyme, does not inhibit [3H]iPr2P-F binding. These data suggest that the leucy-hydrolyzing component of the lens multicatalytic proteinase complex is localized to the 22,000 Mr subunit and is a member of the thiol-dependent subclass of serine proteinases.