Answer
Six proteins found in myofilaments are myosin, actin, troponin , tropomyosin and dystrophin and titin.
Myosin and actin are contractile proteins:
Myosin ; a single myosin molecule is shaped like a golf club and has two intertwined polypeptide chains forming with a shaft-like tail, and a double gulf club head. The heads on one side of the chain bend to the left, and on the other side they bend /angle to the right; the middle zone has no heads
Actin: the actin filament is composed of two intertwined bands of fibrous (F) actin. Each F actin molecule is like a beaded necklace with a string of bead-like G actin subunits.
Work Step by Step
Tropomyosin and troponin are called regulatory proteins:
Troponin is a calcium-sensitive protein that structurally has three subunits -- TN-T, TN-C and TN-l. Its function is to regulate the action of tropomyosin. TN-C binds to calcium; Tn-T binds to tropomyosin and TN-l binds to actin
Tropomyosin consists of two parallel polypeptide chains. It regulates the action of actin filaments and inhibits the force of muscle contractions.
Titin; This protein responsible for the passive elasticity of muscle. It is a very large protein with IgG like domain as well as fibronectin like sequences.
Note . Dystrophin is also a muscle protein. It connects actin filaments to adjacent connective tissues. People with genetically deficient dystrophin develop the genetic disease muscular dystrophy
