Mechanism of Skeletal Muscle Contraction

The sliding filament theory It is well accepted that this is the basic mechanism for muscle contraction. Two groups in England, A.F. Huxley and Niedergerke (1954), and H.E. Huxley and Hanson (1954) are the founders of the theory. Their classical experiments are shown in Figures ME1 and ME 2 Fig. ME1 shows a living frog muscle fiber under the interference microscope. A bands appear dark, I bands are light. The length of the sarcomeres, A and I bands were measured on densitometer tracings. The...

Regulation of Muscle Contraction

The main feature of muscle contraction is the interaction of actin, myosin and ATP. This fundamental process of contraction is regulated by the tropomyosin-troponin-Ca2+ system. According to the current theory, in the resting muscle TM is positioned in the groove of the actin double helix in a way that it sterically blocks the combination of myosin with actin. This is illustrated in Fig. RE1a, which shows a thin filament composed of actin, tropomyosin, TN-C, TN-I, and TN-T. Fig. RE1a. The...

Actin Myosin Interaction

Structural model Both F-actin and myosin are large protein molecules whose interaction takes place at multiple sites in a very specific manner. From the independent X-ray structure of G-actin (Fig. A5) and S1 (Fig. M9) and from the electron density maps of actin filaments decorated with S1, the three-dimensional structure of actoS1 was reconstructed as shown on Fig. AM1. Fig. AMI. Three-dimensional atomic model of F-actin combined with myosin subfragment 1. (From , Geeves and Holmes, with...

Phosphorylation and Dephosphorylation of the 20kDa Myosin Light Chain

Myosin light chain kinase and myosin light chain phosphatase Smooth muscle (as well as skeletal and cardiac muscle) contains myosin light chain kinase (MLCK), activated by Ca2+-calmodulin, the enzyme which transfers the terminal phosphate group of ATP to serine (and or threonine) hydroxyl groups of phosphorylatable light chain (LC) according to the following reaction LC-OH + MgATP2- LC-O-PO32- + MgADP- + H+ (1) Dephosphorylation is brought about by smooth muscle myosin light chain phosphatase...

S

Three radioactive peaks are seen, the first from Pi, the second from ADP, and the third from ATP. For ADP and ATP the absorbance is also shown 85 of the total absorbance is from ADP and 15 from ATP. Since F-actin contains bound-ADP and G-actin contains bound-ATP, the data indicate that 85 of the total actin in this muscle preparation was in the polymeric and 15 in the monomeric form. Determination of the Pi concentration by a colorimetric method showed that the molar ratio of Pi to ADP was...

Historical Development of Muscle Energetics

The lactic acid theory and its disproof Experiments at the beginning of the 20th century were directed to find the chemical substance that provides the energy for muscle contraction. The procedure was as follows One of the two gastrocnemius muscles of a frog was stimulated till fatigue, while the other muscle was resting. Both muscles were analyzed for their chemical constituents. In the stimulated muscle the lactic acid content was increased, its formation was equivalent to the glycogen...