PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Chapter 17 – Cell Organization and Moveme nt I: MicrofilamentsCytoskeleton location and function-Cytoskeleton is dynamic -Cytoskeleton has 3 major filament systems –1) microfilaments – 2) microtubules – 3) intermediate filaments –17.1. Microfilaments and Actin StructuresStructures and locations:Actin is the basic building block; microfilament is actin (and associated proteins) in polymerized form. G-actin versus F-actin17.2. Dynamics of actin filamentsPolymerization of pure G-actin occurs in 3 steps:Actin filaments grow faster on the (+) endTreadmilling:Proteins that aid in polymerization and treadmilling:1) Profilin-2) Cofilin-Proteins that aid in polymerization:3) Thymosin-4Capping proteins: 1) CapZ- 2) Tropomodulin-17.3. Mechanisms of Actin Filament AssemblyNucleating proteins-1) Formins-used to form long filaments2) Arp2/3 complex –Nucleation promoting factor (NPF)Regulation of Arp2/3 complex –17.4. Organization of Actin-Based Structures17.5. Myosins: Actin-Based Motor ProteinsMyosins- motor proteins that can move along actin filaments - powered by ATP hydrolysis.Myosin II – involved in skeletal muscle contractionHydrolysis of 1 ATP needed for each step taken by myosin IIMoves the length of the neck domainRigor mortis:http://www.youtube.com/watch?v=oHDRIwRZRVI17.6. Myosin-Powered MovementsSarcomere:Thick filam ents Thin filam entsMyosin movement along the actin tracks causes muscle contractionOther proteins in the sarcomere:CapZ –Tropomodulin-Nebulin- Titin-Sarcoplasmic reticulum (SR) and Ca+2Release of Ca induces a change in tropomyosin and troponinRegulation in smooth muscle or nonmuscle cellshttp://www.bing.com/videos/search?q=animation+of+muscle+contraction&mid=565A8CD21172073891DE565A8CD21172073891DE&view=detail&FORM=VIRE717.7. Cell Migration: Signaling and Chemotaxis1) Membrane extension2) Cell-substrate adhesions: attachment of stress fibers through integrins. 3) Cell-body translocation: 4) Breaking cell attachments:Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) for movementDominant active proteins are locked into GTP stateAll 3 pathways contribute to regulation of cell migration - in vitro ‘wound healing’