Calcium blocks formation of apoptosome by preventing nucleotide exchange in Apaf-1. Author Qing Bao, Wenyun Lu, Joshua Rabinowitz, Yigong Shi Publication Year 2007 Type Journal Article Abstract Apaf-1 plays an essential role in apoptosis. In the presence of cytochrome c and dATP, Apaf-1 assembles into an oligomeric apoptosome, which is responsible for the activation of procaspase-9 and the maintenance of the enzymatic activity of the processed caspase-9. Regulation of apoptosome assembly by other cellular factors is poorly understood. Here we report that physiological concentrations of calcium ion negatively affect the assembly of apoptosome by inhibiting nucleotide exchange in the monomeric, autoinhibited Apaf-1 protein. Consequently, calcium blocks the ability of Apaf-1 to activate caspase-9. These observations suggest an important role of calcium homeostasis on the Apaf-1-dependent apoptotic pathway. Keywords Humans, Models, Biological, Protein Conformation, Apoptosis, Enzyme Activation, In Vitro Techniques, Homeostasis, Recombinant Proteins, Calcium, Adenine Nucleotides, Apoptosomes, Apoptotic Protease-Activating Factor 1, Caspase 9 Journal Mol Cell Volume 25 Issue 2 Pages 181-92 Date Published 01/2007 Alternate Journal Mol. Cell Google ScholarBibTeXEndNote X3 XML