Cytoskeleton III Chapter 16 Actin binds to many
Cytoskeleton III Chapter 16
Actin binds to many different proteins
Plectin (green) crosslinks intermediate filaments (blue) and microtubules (red)
Cross linking proteins organize different assemblies of actin filaments actin binding sites in red
Actin bundles in a microvillus
Filamin crosslinks actin into 3 -dimensional networks with gel-like properties
Melanoma cells with low filamin levels crawl poorly and tend not to metastasize
When filamin levels are restored the cells move normally and become highly metastatic
Three stages in control of bleeding
Severing existing actin filaments can accelerate assembly of new filaments
Gelsolin severs actin filaments
Actin filament dynamics and platelet activation
Actin filament dynamics and platelet activation
Platelets prior to activation
Activated platelet with large spread lamellipodium
Activated platelet after contraction
Aggregation of platelets
Thrombin is produced at cell surface of platelets
Ca 2+ and diacylglycerol activate protein kinase C
Fibrin emerging from clump of activated platelets
ERM proteins attach actin to plasma membrane
Actin fibers often terminate at focal points
Extracellular signals can effect actin organization, vinuculin identifies focal contacts
Extracellular signals can effect actin organization
Extracellular signals can effect actin organization
Extracellular signals can effect actin organization
Structure of myosin II Myosin head binds and hydrolyzes ATP
Electron micrograph of myosin molecules
Myosin is arranged in thick filaments
Myosin heads are on outside of thick filament
Motor activity is contained completely within myosin heads
Myosin heads can move actin filaments Speed of 4 micrometer per sec
Attached, no ATP Rigor configuration, state acquired during rigor mortis
ATP binding causes release of actin filament
Hydrolysis of ATP causes displacement of head by 5 nm
Release of Pi causes tight binding to new position on actin filament
ADP is released and rigor configuration is assumed once again
Mechanochemical cycle of myosin
DVD clip 74
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