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What sacromeres disks called? What is connected to them?
Z disk and M disk.
- Z dissk is connected to the thin filaments (actin, tropomyosin, troponin).
- M disk is connected to the thick filaments (myosin)
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What is G-actin?
The globular protein with ATP binding site located at the bottom of the deep cleft. This is the monomeric form of actin.
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What is F-actin?
It is the polymeric version of G-actin. Each F-actin monomeric unit has a binding site of a myosin head.
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What are the three regulatory subunits of troponin?
Troponin contains TnC (binds calcium ions), TnI (binds actin) and TnT (binds tropomyosin).
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What is the protein that is the actin-binding protein that regulates actin-myosin interaction?
Tropomyosin.
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In sacromere, each head-rich region of thick filament associated with two actin filaments, one on each side of the thick filament.
Once the nerve impulse reaches the muscle cell, the sarcoplasmic reticulum releases calcium.
The _____ binds to the troponin's Tn__ subunit and causes an allosteric change in the troponin which allows tropomyosin to move, unblocking the binding sites.
Caclium - TnC.
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What are the steps for the muscle contraction?
- 1) Upon ATP hydrolysis, the myosin head has ADP and Pi bound to its nucleotide binding pockets. In this state, the myosin head adopts a high energy "cocked" conformation.
- 2) Myosin weakly binds to the newly uncovered actin-binding sites on the thin filaments.
- 3) The release of phosphate ion leads to a very tight binding of the myosin head to actin. MYosin is the strong binding state.
- 4) The following conformational shift (the power stroke) pulls the thick filament toward the Z-disk. This leads to shortening of the I band and H zone. Thereby, myosin heads "walk" along thin filaments with the cocurrent muscle contraction.
- 5) ADP is released. The release of ADP and inorganic phosphate and the power stroke are coupled.
- 6) ATP is bound in the nucleotide-binding pocket of myosin, which makes myosin release actin and acquire the weak binding state.
- 7) The myosin head then hydrolyzes the bound ATP to ADP and Pi. The release energy is used for moving myosin back into the "cocked" conformation.
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1) Upon ATP hydrolysis, the myosin head has ADP and Pi bound to its nucleotide binding pockets. In this state, the myosin head adopts a high energy _______ conformation.
2) Myosin weakly binds to the newly uncovered ____-binding sites on the _____ filaments.
3) The release of phosphate ion leads to a very tight binding of the myosin head to actin. Myosin is the strong binding state.
4) The following conformational shift (the power stroke) pulls the thick filament toward the Z-disk. This leads to shortening of the I band and H zone. Thereby, myosin heads "walk" along thin filaments with the
cocurrent muscle contraction.
5) ADP is released. The release of ADP and inorganic phosphate and the power stroke are coupled.
6) ATP is bound in the nucleotide-binding pocket of myosin, which makes myosin release actin and acquire the weak binding state.
7) The myosin head then hydrolyzes the bound ATP to ADP and Pi. The release energy is used for moving myosin back into the "cocked" conformation.
- cocked.
- actin-binding sites on the thin filaments.
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1) Upon ATP hydrolysis, the myosin head has ADP and Pi bound to its nucleotide binding pockets. In this state, the myosin head adopts a high energy "cocked" conformation.
2) Myosin weakly binds to the newly uncovered actin-binding sites on the thin filaments.
3) The release of phosphate ion leads to a very tight binding of the myosin head to actin. MYosin is the strong binding state.
4) The following conformational shift (the power stroke) pulls the thick filament toward the Z-disk. This leads to shortening of the I band and H zone. Thereby, myosin heads "walk" along thin filaments with the cocurrent muscle contraction.
5) ADP is released. The release of ADP and inorganic phosphate and the power stroke are coupled.
6) ATP is bound in the nucleotide-binding pocket of myosin, which makes myosin release actin and acquire the weak binding state
7) The myosin head then hydrolyzes the bound ATP to ADP and Pi. The release energy is used for moving myosin back into the "cocked" conformation.
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What is the distance a skeletal muscle myosin head moves?
10-12 nm.
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