Troponin C mediated function is of which of the following?
Ans. is 'c' i.e., Actin o Ca" binds to troponin and this troponin - Ca'2 complex cause lateral displacement of tropomysin.o As a result active sites of actin becomes uncovered and interact with myosin.Important skeletal muscle proteinsMyosin : - Myosin is the protein that constitutes the thick filaments. Myosin of skeletal muscle is myosin-IL Myosin participates in the contractile mechanism and also acts as an ATPase.Actin : - Actin is the major protein of thin filament. It is the actin which slides over myosin during contraction.Tropomyosin : - It is the other protein of thin filament. It covers the active sites (myosin binding sites) on actin. When Ca+2 concentration of cytoplasm (sarcoplasm) is raised, it uncovers the active sites of actin and allow the contraction So, the 'cross-bridge cycling 'is switched off or on by the tropomyosin molecule which slides on the actin molecule to cover or uncover the active sites on it.Troponin : - It is a protein also associated with thin filament. The regulatory action of Ca+2 on tropomysin is mediated by troponin, a Ca+2 binding protein. When the cytoplasmic (sarcoplasmic) Ca+2 concentration rises Ca+2 ions bind to troponin-C. The troponin - Ca+2 complex induces changes in Troponin-I and Troponin-T, which in turn brings about a shift of tropomyosin away from the active sites of actin. When the sarcoplasmic Ca+2 concentration falls, Ca+2 dissociates from troponin-C and tropomyosin slides back on the actin filament to cover the active sites. Thus, the first event during muscle contraction, after cytoplasmic rise in Ca+2 concentration, is binding of troponin C to Ca+2 which trigers the further steps by sliding the tropomysin away from the active sites of actin.o There are additional structural proteins in skeletal muscles,i) Actinin : It binds actin to Z-lines.ii) Titin : It is the largest known protein and connects Z-lines to M-linesand is responsible for passive stiffness of muscle, by limiting range of motion of sarcomere in tension,iii) Desmin : It adds structures to Z-lines in part by binding the Z-lines to plasma membrane.
Dystrophin
Calmodulin
Actin
Calcineurin
Skeletal Muscle: Contraction and Excitation