Lecture 17 (Oct 8)

Lecture 17 (Oct 8) - Biological Sciences 110A Introduction...

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Lecture 17: Muscle and non-muscle motility Myosins: actin-binding ATPase motors Roles for non-muscle myosins Structure and function of muscle Structure of the muscle sarcomere Myosin II - actin interaction drives muscle The Ca 2+ -trigger of muscle contraction Biological Sciences 110A: Introduction to Biology Kendal Broadie Reading in Chapter 9 (368-383) Karp
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Most eukaryotic cells contain a cytoskeleton composed of three protein filament systems Microtubules Intermediate filaments Microfilaments 25 nm 25 nm 25 nm 25 nm dia. Tubulins ( α and β ; MAPs and motor proteins) Vesicle transport, cell polarity, and division 9-12 nm dia. Cell-type specific subunits Elasticity and tensile strength (“rope function”) 6-7 nm dia. Actin (myosin motor, and accessory proteins) Contraction, transport, locomotion and division
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Modulating the assembly and function of actin: actin-binding proteins G-actin F-actin Nucleating proteins Monomer- binding proteins End-capping proteins Side-binding proteins Severing proteins Motors Bundling proteins Cross-linking proteins Thymosin β 4 ARP 2/3 complex Gelsolin/villin α -Actinin Filamin Tropomyosin Myosins CapZ use energy of ATP hydrolysis to walk along actin filaments See Fig. 9.66 Karp
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Cells contain multiple different myosins Small bipolar filaments of ~30-40 molecules. Conventional (Type II) Single-headed “Type I” myosin What roles do different myosins play in cells? All myosins are F-actin binding proteins and ATPases . These proteins use the energy of ATP hydrolysis to move relative to the actin filament . This activity allows a variety of forms of work. Muscle Myosin Structure Two-headed complex
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Non-muscle myosins perform many roles… Type I Myosin: Vesicle transport (e.g. cytoplasmic streaming in plants and algae) Transport vesicle Type I myosin Cargo Vesicle ATPase (ATP --> ADP) See Fig. 9.51 Karp
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Vesicles, ER, and other organelles move along actin bundles in the subcortical cytoplasm Actin and myosin power cytoplasmic streaming in green algae Movement powered by unconventional (type I) myosin
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This note was uploaded on 04/07/2008 for the course BSCI 110B taught by Professor Due during the Spring '08 term at Vanderbilt.

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Lecture 17 (Oct 8) - Biological Sciences 110A Introduction...

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