Biomaterial Database

Interaction of troponin subunits. The interaction between the inhibitory and tropomyosin-binding subunits. 1979

J Horwitz, and B Bullard, and D Mercola

The interaction of troponin-I and troponin-T was demonstrated by circular dichroism and gel filtration. Troponin-I gives a negative circular dichroism band between 300 and 260 nm while troponin-T gives two weak positive bands, one at 290 nm and the other at 263 nm. When troponin-I and troponin-T were mixed, the complex produced a strong negative circular dichroism band with a maximum around 280 nm. This band was most intense with a molar ratio of troponin-T to troponin-I of 1:1. The intensity of the band was 2.4 times that expected from the separate components. The interaction was independent of salt concentration from 0.15 to 0.5 M KCl. Gel filtration on Sephacryl S-200 showed that a stable 1:1 complex was formed between troponin-T and troponin-I. When troponin-C was added to the complex of troponin-T.troponin-I; the reconstituted troponin had a circular dichroism spectrum identical to that of native troponin. The oxidation state of troponin-I was important in reconstituting troponin. Oxidized troponin-I produced less change in the near ultraviolet circular dichroism when added to troponin-T and the troponin-C than did reduced troponin-I. This showed the subunits were not assembled correctly with oxidized troponin-I. When the reconstituted complex was reduced, the circular dichroism was restored to that of native troponin. Troponin reconstituted with oxidized troponin-I did not confer calcium sensitivity on actomyosin ATPase; activity was restored by reducing the complex.

UI	MeSH Term	Description	Entries
D009124	Muscle Proteins	The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessory proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.	Muscle Protein,Protein, Muscle,Proteins, Muscle
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D014335	Tropomyosin	A protein found in the thin filaments of muscle fibers. It inhibits contraction of the muscle unless its position is modified by TROPONIN.	Paramyosin,Miniparamyosin,Paratropomyosin,Tropomyosin Mg,alpha-Tropomyosin,beta-Tropomyosin,gamma-Tropomyosin,Mg, Tropomyosin,alpha Tropomyosin,beta Tropomyosin,gamma Tropomyosin
D014336	Troponin	One of the minor protein components of skeletal and cardiac muscles. It functions as the calcium-binding component in a complex with BETA-TROPOMYOSIN; ACTIN; and MYOSIN and confers calcium sensitivity to the cross-linked actin and myosin filaments. Troponin itself is a complex of three regulatory proteins (TROPONIN C; TROPONIN I; and TROPONIN T).	Troponin Complex,Troponins
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular