The main protein found in animal muscle is myosin. Myosin is a motor protein that plays an essential role in muscle contraction. It interacts with another protein called actin to facilitate the contraction and relaxation of muscle fibers, making it critical to the movement of organisms. Myosin consists of several isoforms, and its structure varies depending on the type of muscle (skeletal, cardiac, or smooth), impacting how muscles function during different activities. Therefore, understanding myosin is fundamental to the study of muscle physiology and biomechanics.