A designed redox-controlled caspase.
Publication Type:Journal Article
Source:Protein Sci, Volume 20, Issue 8, p.1421-31 (2011)
Keywords:Binding Sites, Caspase 7, Crystallography, X-Ray, Disulfides, Escherichia coli, Models, Molecular, Oxidation-Reduction, Protein Conformation, Protein Engineering, Protein Multimerization, Recombinant Proteins
<p>Caspases are a powerful class of cysteine proteases. Introduction of activated caspases in healthy or cancerous cells results in induction of apoptotic cell death. In this study, we have designed and characterized a version of caspase-7 that can be inactivated under oxidizing extracellular conditions and 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 its full function. The inactive loop-locked version of caspase-7 can be readily observed by immunoblotting and 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 Å 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.</p>