Three-Dimensional Image Analysis of the Complex of Thin Filaments and Myosin Molecules from Skeletal Muscle. IV.1 Reconstitution from Minimal- and High-Dose Images of the Actin-Tropomyosin-Myosin Subfragment-1 Complex2

Abstract

Three-dimensional images of the actin-tropomyosin-myosin subfragment-1 (SI) complex were reconstituted from both minimal- and high-dose electron micrographs by using a conventional reconstruction technique. Higher resolution (1/15 Å⁻¹ than those of the previous reconstructions was attained. A multi-domain structure similar to that of the actin-SI complex described in the previous paper (I) was observed and a new diagram of the multi-domain structure of the actin-tropomyosin-SI complex is presented. The shape of SI molecules in the rigor complex was clearly resolved. In a view perpendicular to the filament axis, SI had an axially bent profile; only the tail portion, which was thin but was not small in diameter, was steeply inclined. These features were more prominent in the model from minimal-dose images than that from high-dose images.