topic 6_rivier_252 - Topic 6 Reading Reading Lodish 17.6...

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Topic 6 Reading Reading: Lodish 17.6 and 17.5
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MCB 252 Actin Cytoskeleton A. Properties of Actin B. Role of Actin in Cell Movement C. Regulation of Actin Assembly in Cells D. Stable Actin Structures E. Muscle Cells and Myosin Motors
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Muscle Cells and Myosin Motors 1. Overview of Muscle Cells and Contraction What we Know How we Know it 2. How Do Myosin Motors Work? 3. Additional Proteins and Design Features 4. Regulation of Contraction 5. Additional Uses of Contractile Bundles 6. Myosin Domains 7. Myosin Superfamily
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Recall from MCB150 Sliding Filament Model
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What you need to know and not know
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Muscle Structure
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EM cross-section of muscle fiber Image courtesy Dr. John Heuser, Wash. U Med. School Hexagonal arrays of thick and thin filaments Huxley, 1969 ?
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Muscle Cells and Myosin Motors 1. Overview of Muscle Cells and Contraction What we Know How we Know it 2. How Do Myosin Motors Work? 3. Additional Proteins and Design Features 4. Regulation of Contraction 5. Additional Uses of Contractile Bundles 6. Myosin Domains 7. Myosin Superfamily
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Some highlights of early biochemical work 1859: Kühne isolated a muscle protein that he called “myosin” 1880: T. H. Huxley showed that A bands were lost after treatments which removed myosin; he concluded that A bands were composed mainly of myosin 1938: Albert Szent-Györgyi (1937 Nobel Prize for discovery of Vitamin C) began his studies on muscle
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How does contraction work? First, need an experimental model Albert Szent-Györgyi’s choice: Criteria: need muscle with long, parallel fibers and little connective tissue. It is easy to find the muscle which contains the least connective matter for it is the quantity of connective tissue which decides the culinary value of a muscle, to which it is inversely proportional. The culinary value is expressed numerically on the right side of any menu. A significant difference is always found at the level of. .. Musculus psoas (Psoas muscle: a.k.a. tenderloin)
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Glycerinated muscle fiber prep (Szent- Györgi) Dissect out small bundles of muscle (2mm diameter; 8 cm long); place in 50% glycerol at 0°C then transfer to – 20°C (store for months). Plasma membrane is disrupted; soluble components leak out, but insoluble components of contractile apparatus remain intact. Glycerol prevents formation of ice crystals which could disrupt structure. muscle fiber at rest add ATP contracts Went on to show that purified actin/myosin filaments could contract after addition of ATP
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Different Types of Light Microscopy Bright Field Differential Interference Contrast Phase Contrast Lodish Fig 9-11 pages 380-382
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Sarcomere structure (EM) ( Lodish, 19-22a ) A band I band I band Z disk Z disk H zone M line
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Some terms defined A band: anisotropic I band: isotropic H zone: from Hell, German for “bright” M line: from Mittel, German for “middle” Z disc: from Zwischen, German for “between”
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This note was uploaded on 01/29/2012 for the course MCB 252 taught by Professor Wuebbles during the Spring '08 term at University of Illinois, Urbana Champaign.

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topic 6_rivier_252 - Topic 6 Reading Reading Lodish 17.6...

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