Evolution of myosin filament arrangements in vertebrate skeletal muscle

Abstract

A survey of skeletal muscles throughout craniates shows basic kinds of myosin filament arrangement, simple‐lattice and superlattice, within the A‐band of each sarcomere. Distribution of simple‐ and superlattice arrangements across a phylogeny of craniates suggests that the superlattice arrangement is primitive and that Amia and teleosts are derived in showing simple‐lattice arrangements. Two taxa examined (Scyliorhinus and Acipenser) show both lattice types within the same organism implying that there is not a simple evolutionary transformation of one to the other fiber arrangement. We discuss the possible functional significance of the different lattice types. We believe that the crossbridges may have greater competition for actin binding sites in simple‐lattice muscles compared to the superlattice types. © 1996 Wiley‐Liss, Inc.

Sarcomere lattice geometry influences cooperative myosin binding in muscle

“…Defined above, the multi-filament model consists of four thick filaments and eight thin filaments ( Figure 1A). Multiple thick and thin filaments interact in a hexagonal lattice similar to vertebrate striated muscle [53,54]. The two-filament model is a reduced version of the multi-filament model, where myosin molecules and actin monomers only interact along a single plane [15].…”

“…Two multi-filament model properties permit incorporating hexagonal lattice characteristics of vertebrate skeletal muscle [53,54] ( Figure 1A). The first is implementing thick and thin filaments with longitudinal and rotational characteristics to produce co-linear facing rows of actin and myosin nodes that align at hexagonal vertices.…”

“…Hexagonal Lattice in the Simple-Lattice Model (A-C) Show the detailed three-start, simple-lattice, thick-filament geometry using a similar configuration as described by Figure S2. However, three-start helical properties leave only 1/3 of the crossbridges co-linearly facing thin filaments [54]. Any myosin node (A) is followed by adjacent nodes 14.3 nm (B) and 28.6 nm (C) along the filament.…”

Determination of Myosin Filament Orientations in Electron Micrographs of Muscle Cross Sections

“…The myosin-actin interactions are a function of the geometrical arrangement of these molecules. Of particular importance is the rotational disposition of the myosin filaments within the myosin lattice [5], [6]. The geometry of the myosin lattice is, therefore, of fundamental importance in muscle biology.…”

“…1), where it is devoid of actin filaments and other molecular components, and imaging them in an electron microscope [3], [5]. Careful inspection of such images shows that the myosin filaments are approximately triangular in cross section and that the spatial distribution of their azimuthal rotations varies between muscle types and species [5], [6]. Henceforth, we will refer to the azimuthal rotation of a filament as its "orientation."…”