1. Cytoskeleton III Chapter 16

2. Actin binds to many different proteins

3. Plectin (green) crosslinks intermediate filaments (blue) and microtubules (red)‏

4. Cross linking proteins organize different assemblies of actin filaments actin binding sites in red

6. Actin bundles in a microvillus

8. Filamin crosslinks actin into 3-dimensional networks with gel-like properties

9. Melanoma cells with low filamin levels crawl poorly and tend not to metastasize

10. When filamin levels are restored the cells move normally and become highly metastatic

11. Three stages in control of bleeding

12. Severing existing actin filaments can accelerate assembly of new filaments

13. Gelsolin severs actin filaments

14. Actin filament dynamics and platelet activation

16. Platelets prior to activation

17. Activated platelet with large spread lamellipodium

18. Activated platelet after contraction

19. Aggregation of platelets

20. Thrombin is produced at cell surface of platelets

22. Ca 2+ and diacylglycerol activate protein kinase C

23. Fibrin emerging from clump of activated platelets

24. ERM proteins attach actin to plasma membrane

25. Actin fibers often terminate at focal points

26. Extracellular signals can effect actin organization, vinuculin identifies focal contacts

27. Extracellular signals can effect actin organization

30. Structure of myosin II Myosin head binds and hydrolyzes ATP

31. Electron micrograph of myosin molecules

32. Myosin is arranged in thick filaments

33. Myosin heads are on outside of thick filament

34. Motor activity is contained completely within myosin heads

35. Myosin heads can move actin filaments Speed of 4 micrometer per sec

36. Attached, no ATP Rigor configuration, state acquired during rigor mortis

37. ATP binding causes release of actin filament

38. Hydrolysis of ATP causes displacement of head by 5 nm

39. Release of P i causes tight binding to new position on actin filament

40. ADP is released and rigor configuration is assumed once again

41. Mechanochemical cycle of myosin

42. DVD clip 74