Human caspase-7 activity and regulation by its N-terminal peptide.
Central to the execution phase of apoptosis are the two closely related caspase-3 and -7. They share common substrate specificity and structure, but differ completely in the sequence of their respective N-terminal regions including their N-peptides, a 23-28 residue segment that are removed during zymogen activation. We show that the N-peptide of caspase-7 plays no role in the fundamental activation or properties of the active protease in vitro. However, the N-peptide modifies the properties of caspase-7 in vivo. In ectopic expression experiments, caspase-7 constructs with no N-peptide are far more lethal than constructs that have an uncleavable peptide. Moreover, the N-peptide of caspase-7 must be removed before efficient activation of the zymogen can occur in vivo. These disparate requirements for the N-peptide argue that it serves to physically sequester the caspase-7 zymogen in a cytosolic location that prevents access by upstream activators (caspase-8, -9, and -10). The N-peptide must first be removed, probably by caspase-3, before efficient conversion and activation of the zymogen can occur in vivo.
Denault
Jean-Bernard
JB
Program in Apoptosis and Cell Death Research, The Burnham Institute, La Jolla, California 92122, USA.
Salvesen
Guy S
GS
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D053938:DNA Fragmentation; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D010455:Peptides; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases