Tropomyosin is one of the protein molecules that (together
forms the cylindrical structures called myofibrils that,
together, form muscle
Myofibrils consist of two types of protein filaments, called
filaments, and thick
filaments. Tropomyosin molecules, together with
troponin and actin molecules, form the thin filaments which have a helix
structure - as shown in the diagram below.
Above: Diagram of Tropomyosin molecules within a Thin Filament.
The key function of tropomyosin is to inhibit
muscle contraction by blocking the interaction of actin and myosin (which
is part of the thick filaments), except when influenced by Troponin.
Muscle contraction generally is regulated by the combined actions of
troponin and tropomyosin, which in turn, are controlled by the concentration
of calcium ions in the muscle sarcoplasm.
For further detail about tropomyosin, visit Edinburgh
University's website .