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Dynamic Dissonants Cell and Developmental Biology New York University David Scicchitano Mark Siegal Kris Gunsalus University of Hawaii Steve Robinow Athula.

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Presentation on theme: "Dynamic Dissonants Cell and Developmental Biology New York University David Scicchitano Mark Siegal Kris Gunsalus University of Hawaii Steve Robinow Athula."— Presentation transcript:

1 Dynamic Dissonants Cell and Developmental Biology New York University David Scicchitano Mark Siegal Kris Gunsalus University of Hawaii Steve Robinow Athula Wikramanayake University of Wisconsin, Madison Brian Manske

2 Part I: structure, assembly and dynamics of microfilaments Part II: the cytoskeleton organizes the cytosol and supports the function of other cellular organelles and processes Part III: cytoskeletal filaments form higher-order structures that perform diverse functions Actin Cytoskeleton Teachable Unit

3 Chemical principles govern the behavior of biological macromolecules. Cellular phenomena reflect the collective action of populations of molecules. The same molecule can have multiple, diverse functions within cells. Teaching Challenges

4 Diseases of the cytoskeleton Muscular Dystrophy Dystrophin – muscular degeneration Kartagener Syndrome Axonemal dynein intermediate chain – Infertility due to defective sperm motility – Situs inversus Usher Syndrome myosin VII – deafness Epidermolysis bullosa and bullosa pemphigoid keratin mutation or autoimmune disorder – skin blistering Actin Microtubules Intermediate filaments

5 Are microfilaments the same as F-actin? A. Yes B. No

6 What polymerizes to form microfilaments? A. alpha-tubulin B. intermediate filaments C. beta-tubulin D. G-actin

7 The cytoskeleton is composed of: A. microtubules B. microfilaments C. intermediate filaments D. A and B E. A and C F. B and C G. A, B, and C

8 Are microfilaments the same as F-actin? A. Yes B. No What polymerizes to form microfilaments? A. alpha-tubulin B. intermediate filaments C. beta-tubulin D. G-actin The cytoskeleton is composed of: A. microtubules B. microfilaments C. intermediate filaments D. A and B E. A and C F. B and C G. A, B, and C

9 Are microfilaments the same as F-actin? A. Yes B. No What polymerizes to form microfilaments? A. alpha-tubulin B. intermediate filaments C. beta-tubulin D. G-actin The cytoskeleton is composed of: A. microtubules B. microfilaments C. intermediate filaments D. A and B E. A and C F. B and C G. A, B, and C

10 synonymous to

11 Learning Goals To understand the structure, assembly and dynamics of microfilaments Apply chemical principles to enhance understanding of actin polymerization Predict and understand a biological model of actin polymerization Predict and interpret experimental results

12 G-actin: globular monomer F-actin: filamentous polymer G-actin  F-actin

13 Experiment G-Actin + ATP G-Actin I Results F-actin is present in I only (at steady state) II

14 Additional Experiment G-Actin + ATP* G-Actin + ADP A. No F-actin in either B. F-actin in both C. F-actin in I D. F-actin in II ATP* cannot be hydrolyzed to ADP I II

15 Actual Results G-Actin + ATP G-Actin + ATP* G-Actin + ADP Amount of F-actin at steady state

16 Conclusion For G-actin to form F-actin: A. ATP hydrolysis is necessary. B. ATP is necessary. C. ADP is necessary. D. Either ATP or ADP is necessary. E. Neither ATP nor ADP is needed.

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18 APPPAPPP APPAPP F-actin G-actin Fast Slow

19 Summary 1.G-Actin has four lobes and an ATP binding site 2.In a test tube, add magnesium, sodium, potassium and either ATP or ADP: G-actin  F-actin 3. ATP binding to G-actin provides the best conformation to promote F-actin assembly 4. F-actin has directionality (the two ends are not the same)

20 G-actin ↔ F-actin ATP

21 Actin Dynamics ATP

22 G-actin ↔ F-actin ATP

23 Summary G-actin and F-actin will reach a steady state. The nucleation step is slow.

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25 Acknowledgements Thanks to our facilitators! Randy Phillis Lauren Gollahon


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