Caspase-7 uses an exosite to promote poly(ADP ribose) polymerase 1 proteolysis.

During apoptosis, hundreds of proteins are cleaved by caspases, most of them by the executioner caspase-3. However, caspase-7, which shares the same substrate primary sequence preference as caspase-3, is better at cleaving poly(ADP ribose) polymerase 1 (PARP) and Hsp90 cochaperone p23, despite a lower intrinsic activity. Here, we identified key ...
lysine residues (K(38)KKK) within the N-terminal domain of caspase-7 as critical elements for the efficient proteolysis of these two substrates. Caspase-7's N-terminal domain binds PARP and improves its cleavage by a chimeric caspase-3 by ∼30-fold. Cellular expression of caspase-7 lacking the critical lysine residues resulted in less-efficient PARP and p23 cleavage compared with cells expressing the wild-type peptidase. We further showed, using a series of caspase chimeras, the positioning of p23 on the enzyme providing us with a mechanistic insight into the binding of the exosite. In summary, we have uncovered a role for the N-terminal domain (NTD) and the N-terminal peptide of caspase-7 in promoting key substrate proteolysis.
Mesh Terms:
Amino Acid Motifs, Amino Acid Sequence, Apoptosis, Caspase 3, Caspase 7, Cell Line, Humans, Intramolecular Oxidoreductases, Models, Molecular, Molecular Sequence Data, Poly(ADP-ribose) Polymerases, Protein Structure, Tertiary, Proteolysis, Structure-Activity Relationship, Substrate Specificity
Proc. Natl. Acad. Sci. U.S.A.
Date: Apr. 10, 2012
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