35.10
At the end of metaphase, the bi-oriented chromosomes align at the metaphase plate. During this phase, the cohesin protein ring-complexes hold the sister chromatids together at the centromere region and prevent them from being pulled apart.
Metaphase to anaphase progression is triggered by the cyclin-Cdk-induced phosphorylation of a multisubunit, ubiquitin ligase enzyme – the anaphase-promoting complex, also known as the cyclosome or APC/C. Phosphorylated APC/C binds to a protein, Cdc20, forming an active complex.
The active APC/C complex recognizes an inhibitory protein called securin that is bound to a protease enzyme called separase. Prior to this recognition, securin inhibits the activity of separase.
The active APC/C complex tags securin with the protein ubiquitin, targeting it for proteasomal degradation. Destruction of securin releases separase.
The cyclin-Cdk complex also negatively regulates unbound separase activity through inhibitory phosphorylation.
The active APC/C complex causes the ubiquitination of cyclins, targeting them for proteasomal degradation. The destruction of cyclin removes the enzymatic activity of cyclin-dependent kinases or Cdks.
Inactivation of Cdks all
Bij de overgang van profase naar metafase is er een vermindering van de cohesie langs de chromosomale armen, wat resulteert in de resolutie van zuster…
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