All prokaryotic and eukaryotic DNA polymerases share the same fundamental type of synthetic activity, antiparallel synthesis from 5' to 3' from a template that is 3' to 5'.

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

TLS Online TPP Program

#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

TLS Online TPP Program

#Id: 10518

#Unit 4. Cell Communication and Cell Signaling

Caspases function as homodimers with one domain of each stabilizing the active site of the other; they mediate apoptosis by proteolytic cleavage of selected substrates