that separase cannot function without initially forming the securin-separase complex in most organisms. This is because securin helps properly fold separase into the functional conformation. However, yeast does not appear to require securin to form functional separase because anaphase occurs in yeast even with a securin deletion. On the signal for anaphase, securin is ubiquitinated and hydrolysed, releasing separase for dephosphorylation by the APC-Cdc20 complex. Active separase can then cleave Scc1 for release of the sister chromatids. Separase initiates the activation of Cdc14 in early anaphase and Cdc14 has been found to dephosphorylate securin, thereby increasing its efficiency as a substrate for degradation. The presence of this positive feedback loop offers a potential mechanism for giving anaphase a more switch-like behavior. References Further reading External links https://web.archive.org/web/20041117073907/http://ncbi.nih.gov/entrez/query.fcgi?db=Nucleotide Video by David Morgan explaining action of securin and separin (in MP4 format): http://media.hhmi.org/ibio/morgan/morgan_3.mp4 and in other formats: Mitosis Cell biology EC 3.4.22