Principles of Protein Structure - H. Schultz 1982

Structural Basis of Protein Mechanism, Action, and Function
Definitions

Vast numbers, perhaps even all, of the Organism's activities are rooted in protein function. The organism's overall response to Homeostasis and environmental conditions is ultimately dictated by changes at the atomic or even subatomic level [728]. This chapter attempts to summarize aspects of Cell/13.html">Protein Structure that fall under the categories of mechanism, action or activity, and function.

Mechanism describes the temporal and spatial sequence of fundamental processes that constitute a specific action or reaction. To formulate a mechanism of protein action, one must understand the precise spatial arrangement of atoms and the directional orientation of molecular orbitals. Currently, this is achievable only in exceptional cases, classic Examples being Hemoglobin (Sec. 10.3) and Chymotrypsin (Sec. 11.2). The question pertaining to mechanism is: How does the protein work?

METABOLISM/2.html">THE CONCEPT OF action, or activity, refers to the most observable manifestations of protein properties. For instance, the action of chymotrypsin is to cleave a peptide or polypeptide. The question pertaining to action is: What does the protein do?

Biological function is THE CONTRIBUTION OF a constituent element to the operation of the system as a whole. This implies that protein function must be studied in relation to higher levels of the functional hierarchy [729]. In the case of hemoglobin, for example, these higher levels include Circulation and metabolism. Chymotrypsin fulfills a specific function within the Digestive System by breaking down dietary Proteins, as well as a protective role in the body's defense system by inactivating harmful Polypeptides (such as certain Hormones, toxins, and viral proteins) before they can breach the epithelial barrier. The question pertaining to function: What is the purpose of the protein?

In the following sections, using Enzymes as examples, we discuss the known Mechanisms of Protein action. At the end of the chapter, we examine the operation of a specific organ—Skeletal Muscle—at the level of protein action and function.



Last update: 06/08/2026

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