A new model for the transition of APAF-1 from inactive monomer to caspase-activating apoptosome.
The cytosolic adaptor protein Apaf-1 is a key player in the intrinsic pathway of apoptosis. Binding of mitochondrially released cytochrome c and of dATP or ATP to Apaf-1 induces the formation of the heptameric apoptosome complex, which in turn activates procaspase-9. We have re-investigated the chain of events leading from monomeric autoinhibited Apaf-1 to the functional apoptosome in vitro. We demonstrate that Apaf-1 does not require energy from nucleotide hydrolysis to eventually form the apoptosome. Despite a low intrinsic hydrolytic activity of the autoinhibited Apaf-1 monomer, nucleotide hydrolysis does not occur at any stage of the process. Rather, mere binding of ATP in concert with the binding of cytochrome c primes Apaf-1 for assembly. Contradicting the current view, there is no strict requirement for an adenine base in the nucleotide. On the basis of our results, we present a new model for the mechanism of apoptosome assembly.
Reubold
Thomas F
TF
Max Planck Institute for Molecular Physiology, 44227 Dortmund, Germany.
Wohlgemuth
Sabine
S
Eschenburg
Susanne
S
D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D017209:Apoptosis; D053478:Apoptosomes / Q000378:metabolism*; D053477:Apoptotic Protease-Activating Factor 1 / Q000737:chemistry*; D053453:Caspase 9 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D006868:Hydrolysis; D007313:Insecta; D008954:Models, Biological; D009711:Nucleotides / Q000737:chemistry
C506592:APAF1 protein, human; D053478:Apoptosomes; D053477:Apoptotic Protease-Activating Factor 1; D009711:Nucleotides; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D053453:Caspase 9; D020169:Caspases