AS.020.305 Midterm: cell bio final study sheet (dragged) 3
Document Summary
Full activation of the cyclin-cdk complex then occurs when a separate kinase, the cdk-activating kinase (cak), phosphorylates an amino acid near the entrance of the cdk active site. This causes a small conformational change that further increases the activity of the cdk, allowing the kinase to phosphorylate its target proteins effectively and thereby induce specific cell-cycle events. The*cellacycle*control*system*depends*on*cyclical*proteolysis: whereas activation of specific cyclin-cdk complexes drives progression through the start and. Many of these enzymes are used in numerous cell processes to stimulate the proteolytic destruction of specific regulatory proteins. They transfer multiple copies of the small protein ubiquitin to specific target proteins, resulting in their proteolytic destruction by the proteasomes. Other ubiquitin ligases mark proteins for purposes other than destruction: the apc/c catalyzes the ubiquitylation and destruction of two major proteins. The first is securln, which normally protects the protein linkages that hold sister chromatid pairs together in early mitosis.
