Principles of Protein Structural Organization - H. Schultz 1982

Structural Foundations of Protein Mechanism, Action, and Function
Skeletal muscle is a system in which protein action can be linked to the overall activity of the organ

Three properties of Skeletal Muscle make it a convenient subject for Structural and functional analyses: (a) relative insensitivity to manipulation; (b) large quantities of typical Proteins, with a muscle Cell containing 10% Myosin, 3.5% Actin, 2% Tropomyosin plus troponin, and 2% Ca²⁺-transporting ATPase; and (c) the highly ordered geometric arrangement of contractile proteins. By applying techniques such as low-angle X-ray scattering and high-resolution Electron Microscopy in combination with biochemical and physiological Methods of Analysis, it is possible to correlate details of molecular Structure with the overall activity of the organ [755, 758].

Recognition, response, and regulation are key aspects of the BIOLOGICAL Functions OF protein structures within The Cell. Although the muscle cell is highly specialized, it nonetheless exhibits most of the traits typical of living systems (Table 11.1). For instance, it possesses the capacity for activity and for the control of that activity [687]. A signal entering this system (a Nerve Impulse) triggers a powerful response (movement or tension) that is tightly regulated in time, space, and intensity, and is coordinated with functionally related systems, such as the processes supplying chemical energy. In this respect, the functions of these proteins fall under the main categories of cell biology: recognition (which molecules does the protein interact with?), response (how does the protein react to a stimulus or signal?), and regulation (How is the protein's activity controlled, or what process exerts this control?). However, all these terms describe different facets of Protein Structure, and consequently, no strict boundaries can be drawn between them.