During Attenuation, Region 3-4 forms hairpin then second hairpin is formed between Region 1-2

TLS Online TPP Program

#Id: 10512

#Unit 4. Cell Communication and Cell Signaling

EGL-1 protein binds to CED-9, alters its conformation, and catalyzes the release of CED-4 from CED-9

TLS Online TPP Program

#Id: 10513

#Unit 4. Cell Communication and Cell Signaling

Four freed CED-4 dimers combine to form a CED-4 octamer, which binds two molecules of the CED-3 zymogen (an enzymatically inactive precursor) triggers the formation of the active CED-3 protease

TLS Online TPP Program

#Id: 10514

#Unit 4. Cell Communication and Cell Signaling

In mammals

XIAP (inhibitor of apoptosis proteins) restrain both initiator and effector caspases

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#Id: 10515

#Unit 4. Cell Communication and Cell Signaling

XIAP has N-terminal BIR domains: 

BIR2 - binds to and inhibits caspase-3 and caspase-7

BIR3 - binds to and inhibits initiator caspase-9

TLS Online TPP Program

#Id: 10516

#Unit 4. Cell Communication and Cell Signaling

Bax or Bak oligomers leads to the release of SMAC/DIABLOs, from the mitochondrial IMS which binds to XIAP in the cytosol & blocking XIAP from binding to caspases. 

TLS Online TPP Program

#Id: 10517

#Unit 4. Cell Communication and Cell Signaling

Caspases

are so named because they contain a key cysteine residue in the catalytic site and selectively cleave proteins at sites just C-terminal to aspartate residues