What roles do contractile, regulatory, and structural proteins play in muscle contraction and relaxation?
thewriter Teacher College – Senior Assistant Editor Expert $(document).ready(function() { $(‘a.toggle_expert_titles’).click(function() { $(‘#show_expert_titles’).toggle(); return false; }); }); Muscle fibers or myofibrils are formed of three types of proteins which are (1) contractile, (2) regulatory, and (3) structural. Contractile proteins are the force generators of muscle contraction. The two contractile proteins in myofibrils are actin which is part of thin filament and myosin, which is part of the thick filament. The regulatory proteins troponin and tropomysium, which are a part of the thin filament, are involved in starting or stopping muscle contraction. When the muscle is relaxed, tropomysium blocks the myosin-binding sites on the actin proteins; this prevents the muscle from contracting. Troponin holds the tropomysium proteins in place. This is changed when calcium enters the muscle fibers; it binds to the troponin molecule, and moves the tropomysium away from the myosin-bind
