Biology 2382B Lecture Notes - Cdk Inhibitor, Nuclear Membrane, Prophase
12 Feb 2014
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Document Summary
Wee1 is a kinase that phosphorylates cdk leading to its inactivation, while cdc25 is a phosphatase that removes the inhibitory phosphate group (left by wee1) from cdk and promotes its activation. In the recessive elongated fission yeast cells, these mutants were long and unable to engage mitosis (increased g2), because their mutation either resulted in an excess of wee1 or a deficit of cdc25 (leading to inappropriately inactive mpf). Factor: wee1, an inhibitory kinase, introduces a phosphate group to the tyrosine at position 15 (y15) on bound cdk, so the mpf complex remains inactive (key to discouraging premature mitosis). In the next step, cak (cyclin activating kinase) phosphorylates the threonine at position 161 (t161) on bound cdk, so the mpf complex is somewhat activated (not optimal for engaging mitosis). It is only when the activating phosphatase cdc25 removes the phosphate on y15 that the. Mpf is fully activated and ready to promote mitotic division.
