CapZ, Tropomodulin, Nebulin and Titin

Each myosin thick filament is surrounded by 6 thin microfilaments (actin filaments) for it to work on. The plus ends of the actin filaments are capped by CapZ which allows them to be buried in the Z disk. The minus ends of the actin filaments are capped by tropomodulin. Nebulin is a large molecule that has repeated actin binding sites and is thought to determine the length of the actin filaments. Titin is one of the biggest proteins in the human body and is an elastic molecule that prevents over-stretching of the sacromere. When you pull a muscle you rip the titin protein apart.