Two-dimensional electrophoresis of troponin complex with nonequilibrium pH gradient-sodium dodecyl sulfate polyacrylamide slab gel.

A two-dimensional electrophoresis procedure for the separation and analysis of troponin subunits is described in which the protein solution supplemented with 50 mM each of both glutamic and aspartic acids is subjected to nonequilibrium pH gradient electrophoresis in the first dimension. Complete dissolution and gelation of the sample with agarose are essential for analysis of constituent proteins of cardiac myofibrils. Electrophoresis in the first dimension gel is carried out for a relatively short time, 2-3 h. In combination with sodium dodecyl sulfate slab gel electrophoresis (second dimension), three subunits, troponin T, troponin I, and troponin C, of dog cardiac troponin-tropomyosin complex and myofibrils can be simultaneously analyzed quantitatively on a slab gel. The contents of troponin and tropomyosin of cardiac myofibrils were 275 +/- 34 pmol/mg of myofibrillar protein. The molar ratio of troponin T, troponin I, troponin C, and tropomyosin was close to 1 : 1 : 1 : 1 in troponin-tropomyosin complex and myofibrils.