title: The holo-apoptosome: activation of procaspase-9 and interactions with caspase-3.
abstract: Activation of procaspase-9 on the apoptosome is a pivotal step in the intrinsic cell death pathway. We now provide further evidence that caspase recruitment domains of pc-9 and Apaf-1 form a CARD-CARD disk that is flexibly tethered to the apoptosome. In addition, a 3D reconstruction of the pc-9 apoptosome was calculated without symmetry restraints. In this structure, p20 and p10 catalytic domains of a single pc-9 interact with nucleotide binding domains of adjacent Apaf-1 subunits. Together, disk assembly and pc-9 binding create an asymmetric proteolysis machine. We also show that CARD-p20 and p20-p10 linkers play important roles in pc-9 activation. Based on the data, we propose a proximity-induced association model for pc-9 activation on the apoptosome. We also show that pc-9 and caspase-3 have overlapping binding sites on the central hub. These binding sites may play a role in pc-3 activation and could allow the formation of hybrid apoptosomes with pc-9 and caspase-3 proteolytic activities.
authors.affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118-2526, USA.
authors.forename: Shujun
authors.initials: S
authors.lastname: Yuan
authors.forename: Xinchao
authors.initials: X
authors.lastname: Yu
authors.forename: John M
authors.initials: JM
authors.lastname: Asara
authors.forename: John E
authors.initials: JE
authors.lastname: Heuser
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ludtke
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Akey
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D053478:Apoptosomes / Q000737:chemistry*; D053477:Apoptotic Protease-Activating Factor 1 / Q000737:chemistry; D053468:CARD Signaling Adaptor Proteins / Q000737:chemistry / Q000235:genetics; D053148:Caspase 3 / Q000737:chemistry*; D053453:Caspase 9 / Q000737:chemistry*; D004789:Enzyme Activation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D013917:Thrombin / Q000737:chemistry
chemical_list: C506592:APAF1 protein, human; D053478:Apoptosomes; D053477:Apoptotic Protease-Activating Factor 1; D053468:CARD Signaling Adaptor Proteins; D013917:Thrombin; D053148:Caspase 3; D053453:Caspase 9