Engineered hybrid dimers: tracking the activation pathway of caspase-7.
Caspase-7 is an obligate dimer of catalytic domains, with generation of activity requiring limited proteolysis within a region that separates the large and small chains of each domain. Using hybrid dimers we distinguish the relative contribution of each domain to catalysis by the whole molecule. We demonstrate that the zymogen arises from direct dimerization and not domain swapping. In contrast to previous conclusions, we show that only one of the catalytic domains must be proteolyzed to enable activation. The processed domain of this singly cleaved zymogen has the same catalytic activity as a domain of fully active caspase-7. A transient intermediate of singly cleaved dimeric caspase-7 can be found in a cell-free model of apoptosis induction. However, we see no evidence for an analogous intermediate of the related executioner caspase-3. Our study demonstrates the efficiency by which the executioner caspases are activated in vivo.
Denault
Jean-Bernard
JB
The Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.
Békés
Miklós
M
Scott
Fiona L
FL
Sexton
Kelly M B
KM
Bogyo
Matthew
M
Salvesen
Guy S
GS
D000595:Amino Acid Sequence; D017209:Apoptosis; D001224:Aspartic Acid / Q000378:metabolism; D053179:Caspase 7; D020169:Caspases / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D053418:Death Domain Receptor Signaling Adaptor Proteins; D019281:Dimerization; D004789:Enzyme Activation; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D015202:Protein Engineering; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000378:metabolism
D053418:Death Domain Receptor Signaling Adaptor Proteins; D011994:Recombinant Proteins; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D001224:Aspartic Acid; C505520:CASP7 protein, human; D053179:Caspase 7; D020169:Caspases