muscle protein

muscles protein ppt

1. 1 MUSCLE PROTEINS Presented by;- MAAZ UL HAQ c.L gupta eye institute

2. MUSCLE PROTEIN Muscle mass is composed of protein. Largely contributed by structural proteins namely actin, myosin, and the actin cross-linking proteins, tropomyosin and troponin. Muscle also contains other proteins - myoglobin, collagen, enzymes etc. 2

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4. ACTIN Major constituent of thin filaments of sarcomere. It exists in two forms – Monomeric G- actin Polymeric F- actin . G- actin constitutes about 25% of the muscle proteins by weight. In the presence of Mg ions, G- actin polymerizes to form an insoluble double helical F- actin with a thickness of 6-7 nm. 4

5. FUNCTION OF ACTIN Some major roles of actin include: Being the structural makeup and support of the cytoskeleton. Dividing and producing in order to enble cells to move spontaneously and actively. Serving as a supportive framework for myosin protein during muscle contraction. 5

6. TROPOMYOSIN AND TROPONIN Cross-linking proteins found in association with actin. Although, minor in terms of mass, they are important in terms of their function. Tropomyosin, composed of two chains, attaches to F-actin in the grooves . Troponi consists of three polypeptide chain- troponin T, tropinin I, troponin C 6

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8. MYOSIN Myosins are actually a family of proteins with about 15 member . The myosin that is predominantly present in muscle is myosin ll . myosin constitute approximately 55% of muscle , and found in thick filaments. Myosin is composed of six polypeptide chains. lt contains one pair of heavy (H) chains, and two pairs of light (L) chains. 8

9. FUNCTION OF MYOSIN Myosin has three important functions as follows: Constituent of thick filament of muscle fiber. The amino terminal globular ends of myosin exhibit adenosine triphosphatase (ATPase) activity, It hydro lyzes ATP to ADP + Pi and provides free energy for muscle contracrion. Myosin interacts with actin and generates the force that moves the thick and thin filament past each other. 9

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11. Light and heavy meromyosins When myosin is digested with trypsin, two fragments namely LMM and HMM ar e produced . Ligh meromyosin represents the a-helical fibres of the tail of myosin, and cannot bind to F-actin. Heavy meromyosin contains the fibrous and globular portions of myosin. HMM inhibit ATPas e activitv and binds to F - actin. 11

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13. MUSCLE CONTRACTION During the relaxation phase of muscle contraction n, the S-1 head of myosin hydrolyses ATP to ADP and Pi. On contraction, the muscle gets stimulatet to finally form actin myosin-ADP-Pi complex. The next step is the power s tr oke whic h drives movement of actin filaments over myosin filaments . This is followed by the release of ADPand Pi, and a conformation change in myosin The actin-myosin complex is in a low energ y state. 13

14. A fresh molecule of ATP now binds to form actin-myosin ATP complex. 14

15. Sources o f AT P for Muscle contraction ATP is a constant source of energy for muscle contraction and relaxation cycle. ATP can be generated from the following ways. By substrate level phosphorylation of glycolysis using glucose or glycogen. By oxidative phosphorylation. From creatine phosphate. 15

16. Muscles Disease Museular Dystrophy - Muscular dystrophy is a hereditary disease in Which muscles progressively deteriorate. This is Caused by mutations in the gene coding for the protein dystrophin. Muscular dystrophy refers a group of disorders that involve a progressive loss of muscle mass and consequent loss of strength.  16

17. THANK YOU...... 17