Structure of the thick filament and M-line

Items covered in this animation:

• Titin, a sarcomeric structural protein which is the largest polypeptide known at 3 MDa. It stretches the entire length of the half sarcomere from M-line to Z-line and controls both the length of the sarcomere and it's elasticity.
• Myomesin, another structural protein that is found in the M-line and helps titin and myosin maintain their 3-dimensional structure which is shown in the animation.
• Creatine Kinase, this is also found in the M-line and is the enzyme which transfers the phosphate group from creatine phosphate to ADP, and is therefore vital to the energetics of muscle contraction.
• C-protein, maintains the width of the thick filaments by restricting them to 200-400 molecules each.
• MLCK (Myosin Light Chain Kinase) this can bind to the thick filament and phosphorylates the light chain of the myosin. This serves to sensitize the myosin to calcium activation.