Abstract
High resolution information about the three-dimensional (3D) structure of myosin filaments has always been hard to obtain. Solving the 3D structure of myosin filaments is very important because mutations in human cardiac muscle myosin and its associated proteins (e.g. titin and myosin binding protein C) are known to be associated with a number of familial human cardiomyopathies (e.g. hypertrophic cardiomyopathy and dilated cardiomyopathy). In order to understand how normal heart muscle works and how it fails, as well as the effects of the known mutations on muscle contractility, it is essential to properly understand myosin filament 3D structure and properties in both healthy and diseased hearts.The aim of this review is firstly to provide a general overview of the 3D structure of myosin thick filaments, as studied so far in both vertebrates and invertebrate striated muscles. Knowledge of this 3D structure is the starting point from which myosin filaments isolated from human cardiomyopathic samples, with known mutations in either myosin or its associated proteins (titin or C-protein), can be studied in detail. This should, in turn, enable us to relate the structure of myosin thick filament to its function and to understanding the disease process. A long term objective of this research would be to assist the design of possible therapeutic solutions to genetic myosin-related human cardiomyopathies.
Highlights
Solving the 3D structure of myosin filaments is very important because mutations in human cardiac muscle myosin and its associated proteins are known to be associated with a number of familial human cardiomyopathies
The aim of this review is firstly to provide a general overview of the 3D structure of myosin thick filaments, as studied so far in both vertebrates and invertebrate striated muscles
The sarcomere is approximately 2–3 mm in length, and consists of overlapping parallel arrays of actin [thin] filaments and myosin [thick] filaments. It is the cyclic interaction between these two sets of filaments, fuelled by the hydrolysis of adenosine triphosphate (ATP), which generates a mechanical force to make the actin and myosin filaments slide past each other during muscle contraction, shortening the sarcomere length without any change in length of either kind of filament
Summary
When viewed under a microscope, myofibrils have distinct features of alternating light and dark bands running along their lengths (Figure 1c). The myosin filaments of scallop striated adductor muscles are seven-stranded helical structures with an axial repeat of 1440 A (Figure 7c).[38,39,40,41] The interesting thing is that the axial separation between the myosin heads crown levels in the myosin filaments in each of these different vertebrate and invertebrate species is about 143 –145 A (Figure 7a-c). This implies that this value of axial spacing is important within the context of the full sarcomere, where there are a number of actin filaments surrounding each myosin filament. As a result of studying the crystal structures of myosin head, understanding of muscle contraction evolved from the swinging crossbridge model to a swinging lever arm hypothesis.[48]
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