Abstract
The interaction of fructose diphosphate aldolase with F-actin, F-actin-tropomyosin, and F-actin-tropomyosin-troponin has been studied by using negative staining. In the absence of troponin, minor aggregates of aldolase and the F-actin filaments are formed. A well-ordered lattice structure is only formed in the case of the fully reconstituted filament when the filament-to-filament spacing is 18nm, and the cross-bridge spacing is 38.7 nm. Evidence is presented that the lattice is due to an interaction between troponin and aldolase. The minimum subunit structure of troponin, still capable of giving rise to a lattice, is the troponin-IT complex, which indicates that troponin-C is not involved in aldolase binding.