PMID: 21674661

Authors:

Witkowski WA, Hardy JA

Title:

A designed redox-controlled caspase.

Journal:

Protein Sci. 2011 Jun 14. doi: 10.1002/pro.673.

Abstract:

Caspases are a powerful class of cysteine proteases. Introduction of activated caspases in healthy or cancerous cells results in induction of apoptotic cell death. We have designed and characterized a version of caspase-7 that can be inactivated under oxidizing conditions like those found extracellularly, then reactivated under reducing, intracellular conditions. This version of caspase-7 is allosterically inactivated when two of the substrate-binding loops are locked together via an engineered disulfide. When this disulfide is reduced, the protein regains full function. The inactive loop-locked version of caspase-7 can be readily observed by immunoblotting and by mass spectrometry. The reduced and reactivated form of the enzyme observed crystallographically is the first caspase-7 structure in which the substrate-binding groove is properly ordered even in the absence of an active-site ligand. In the reactivated structure, the catalytic dyad cysteine-histidine are positioned 3.5 A apart in an orientation that is capable of supporting catalysis. This redox-controlled version of caspase-7 is particularly well-suited for targeted cell death in concert with redox-triggered delivery vehicles.