The structural protein associated with thin filaments that serves to anchor them to the Z disc is called actinin.
Actinin plays a crucial role in muscle contraction and overall muscular structure. This protein is found in the Z disc of sarcomeres, where it binds to the thin filaments (composed mainly of actin) and helps maintain the alignment of the filaments so that muscle fibers can contract effectively. By anchoring the ends of the thin filaments, actinin contributes to the stability of the entire sarcomere structure, ensuring that muscle movements are coordinated and efficient.