Ultracentrifugal studies of mixtures of aldolase and the troponin–tropomyosin complex from bovine muscle showed the existence of a labile interaction between these two myofibrillar constituents in imidazole buffers, pH6.8, I 0.02–0.10 (mol/l), and the suppression of the reaction by fructose 1,6-diphosphate. Analysis of the sedimentation-velocity patterns suggests the binding of more than 2 molecules of troponin–tropomyosin/molecule of aldolase. The results illustrate the necessity of considering additional or alternative sites to F-actin to account for the observed binding of aldolase to the thin filaments of skeletal muscle.
