Analysis of activator-binding sites on the APC/C supports a cooperative substrate-binding mechanism.
The anaphase-promoting complex or cyclosome (APC/C) is a ubiquitin ligase essential for the completion of mitosis in all eukaryotic cells. Substrates are recruited to the APC/C by activator proteins (Cdc20 or Cdh1), but it is not known where substrates are bound during catalysis. We explored this problem by analyzing mutations ... in the tetratricopeptide-repeat-containing APC/C subunits. We identified residues in Cdc23 and Cdc27 that are required for APC/C binding to Cdc20 and Cdh1 and for APC/C function in vivo. Mutation of these sites increased the rate of activator dissociation from the APC/C but did not affect reaction processivity, suggesting that the mutations have little effect on substrate dissociation from the active site. Further studies revealed that activator dissociation from the APC/C is inhibited by substrate, and that substrates are not bound solely to activator during catalysis but interact bivalently with an additional binding site on the APC/C core.
Mesh Terms:
Amino Acid Motifs, Amino Acid Sequence, Binding Sites, Cell Cycle Proteins, Enzyme Activation, Models, Biological, Molecular Sequence Data, Mutation, Protein Binding, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Analysis, Protein, Ubiquitin-Protein Ligase Complexes
Amino Acid Motifs, Amino Acid Sequence, Binding Sites, Cell Cycle Proteins, Enzyme Activation, Models, Biological, Molecular Sequence Data, Mutation, Protein Binding, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Analysis, Protein, Ubiquitin-Protein Ligase Complexes
Mol. Cell
Date: Apr. 10, 2009
PubMed ID: 19362536
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