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

3. 3

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 wei
ght.
• In the presence of Mg ions, G- actin polymerizes to form an in
soluble 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 contr
action.
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 t
he grooves .
• Troponi consists of three polypeptide chain-
troponin T, tropinin I, troponin C
6

7. 7

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 th
ick 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 tri
phosphatase (ATPase) activity, It hydrolyzes ATP to ADP + Pi and p
rovides free energy for muscle contracrion.
• Myosin interacts with actin and generates the force that moves t
he thick and thin filament past each other.
9

10. 10

11. Light and heavy meromyosins
• When myosin is digested with trypsin, two fragments namely LMM
and HMM are 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 my
osin.
• HMM inhibit ATPase activitv and binds to F-actin.
11

12. 12

13. MUSCLE CONTRACTION
• During the relaxation phase of muscle contractionn, the S-1 head
of myosin hydrolyses ATP to ADP and Pi.
• On contraction, the muscle gets stimulatet to finally form actin my
osin-ADP-Pi complex.
• The next step is the power stroke which 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-myosi
n complex is in a low energy state.
13

14. • A fresh molecule of ATP now binds to form actin-myosin ATP c
omplex.
14

15. Sources of ATP 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 protei
n dystrophin.
• Muscular dystrophy refers a group of disorders that involve a pro
gressive loss of muscle mass and consequent loss of strength.
16

17. THANK YOU......
17