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Dystrophin and Associated Muscle Proteins

Dystrophin and Associated Muscle Proteins. Kevin Cashman Biol. 317 March 22, 2006. Dystrophin. A 427-kDa cytoskeletal protein and a member of the β -spectrin/ α -actinin protein family Has an actin binding domain to bind to F-actin myofilaments

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Dystrophin and Associated Muscle Proteins

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  1. Dystrophin and Associated Muscle Proteins Kevin Cashman Biol. 317 March 22, 2006

  2. Dystrophin • A 427-kDa cytoskeletal protein and a member of the β-spectrin/α-actinin protein family • Has an actin binding domain to bind to F-actin myofilaments • Gene contains 79 exons in which with a high rate of alternate splicing on the C-terminus • Associates with many other proteins to form the dystrophin glyco-protein complex (DGC)

  3. List of Dystrophin Associated Proteins • β-dystroglycan= sacrolemma spanning protein that dystrophin binds to • F-actin= N-terminus of dystrophin binds to • β-dystrobrevin= sacroplasmic protein that binds to dystrophin and the sarcoglycan complex • Sarcoglycan complex= α,β,γ,δ-sarcoglycan proteins embedded into the sarcolemma that associates with β-dystrobrevin, and α and β-dystroglycan primarily.

  4. List of Dystrophin Associated Proteins (cont.) • α-dystroglycan= associates to β-dystroglycan and laminin-2 outside of the sacrolemma • laminin-2= binds to the extracellular matrix and accociates with α-dystroglycan

  5. Functions of DGC • Two functions: • To act as a shock-like complex to protect the muscle fiber’s sacrolemma from stress induced fractures during muscle contractions • Associated proteins, nitric oxide synthase (NOS) and growth factor receptor bound protein 2 (GRB2), maintain cell viability and regulate the functions of the cytoskeleton.

  6. Problems • Mutations in thedystrophin gene can cause truncated proteins that get low productions levels, or the dystrophin protein isn’t produced at all. Without this the complex cannot bind to F-actin and fulfill its role. • There are hundreds of mutations associated with the dystrophin gene in the majority of the exons and many of the mutations cause a type of dystrophy. • Duchenne muscular dystrophy (absent) and Becker muscular dystrophy (truncated) are two of the most severe mutations.

  7. References • The Dystrophin Story, http://compbio.berkeley.edu/people/ed/rust/Dystrophin.html • Function and Genetics of Dystrophin and Dystrophin-Related Proteins in Muscle, Blake et al (2002); Physiological Reviews, 82: 291-329. • http://www.mja.com.au/public/issues/179_09_031103/byr10494_fm-1.gif • http://images.google.com/imgres?imgurl=http://embryology.med.unsw.edu.au/DNA/images/dystrophin.gif&imgrefurl=http://embryology.med.unsw.edu.au/DNA/SWISS-PROTdystrophin.htm&h=224&w=207&sz=13&tbnid=bIU8EqiYBpH9nM:&tbnh=102&tbnw=94&hl=en&start=5&prev=/images%3Fq%3DDystrophin%26svnum%3D10%26hl%3Den%26lr%3D • An Introduction to Human Molecular Genetics (2005), Jack Pasternak; Miley-Liss Inc., New Jersey.

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