Lecture 21-W11 - Lecture 21 (3-07-11) Notes I. The...

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Lecture 21 (3-07-11) Notes I. The discovery of Mitotis Promoting Factor (MPF) A. Microinjection of cytosol into interphase cells. 1. When cytosol from interphase cells was injected, nothing happened. 2. When cytosol from mitotic cells was injected, the interphase cells showed hallmarks of mitotis (formation of mitotic spindle; breakdown of nuclear envelope). B. These experiments indicated that there is something in mitotic cell cytosol that controls the G 2 to M phase transition. C. The active ingredient (MPF) was found to consist of two proteins. 1. One was a protein kinase (Cdk). 2. The other was a protein (M-cyclin) that binds to Cdk (forming M-Cdk complex, another name for MPF). D. The expression of these two factors is different throughout the cell cycle. 1. Cdk is expressed at constant levels. 2. M-cyclin levels are low at the end of M-phase and then increases to a peak at the end of G 2 . 3. Cdk is only active when bound to M-cyclin, so MPF activity is low throughout the cell cycle and high at the end of G 2 . 4. MPF phosphorylates proteins, initiating mitosis. II. How do protein kinases work
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This note was uploaded on 02/13/2012 for the course BIO 172 taught by Professor Clark during the Winter '08 term at University of Michigan.

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Lecture 21-W11 - Lecture 21 (3-07-11) Notes I. The...

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