Figure 16.2 Molecular mechanism of Skeletal muscle contraction

In smooth muscles, troponin is replaced by p-light chain protein.  In sarcoplasm, calmodulin and myosin-light chain kinase are present. In excited or action potential generated condition, sarcoplasmic calcium level increases calmodulin which immediately bind with four calcium level. Ca++-calmodulin complex immediately binds with the enzyme p-light chain kinase. P-light chain kinase-calmodulin complex actively phosphorylate the p-light chain. Phosphorylated p-light chain readily dismantle from the actin filament. Immediately, myosin bind with actin after ATP lysis and results contraction of actin filament. When ATP binds with myosin, it again disassemble from the actin filament and p-light chain bind back to the actin to lead relaxed condition.