Which proteins are primarily associated with the muscle cytoskeleton?

The proteins primarily associated with the muscle cytoskeleton include alpha actinin, titin, and nebulin, which play crucial roles in maintaining the structure and function of muscle fibers.

Alpha actinin is critical for organizing actin filaments within the Z-disc of the sarcomere, helping to anchor them and facilitate muscle contraction. Titin is the largest known protein and extends from the Z-disc to the M-line of the sarcomere, functioning as a molecular spring that contributes to the passive elasticity of muscle, providing structural integrity and helping maintain the alignment of myosin and actin filaments during muscle contraction. Nebulin acts as a template for the lengths of the actin filaments in the sarcomere and plays a role in regulating actin filament assembly and stability.

These functions are essential for the proper functioning of skeletal and cardiac muscle tissues, supporting not only mechanical interactions during contractions but also signaling pathways related to muscle growth and repair.

The other options include proteins that are associated with different structural roles in various tissues. Collagen, elastin, and keratin are key components of connective tissues, skin, and hair but are not specific to muscle cytoskeletal function. Actin, myosin, and troponin, while important