Protein function machinery: from basic structural units to modulation of activity

- Closed loops are universal basic units of globular proteins.
- Enzymatic functions are combined from elementary functional loops.
- Structural dynamics is the cornerstone of the protein function and its regulation.
- Intrinsic disorder, intermolecular interactions, and allostery work in modulation of protein activity.
- Post-translational modification is an intricate mechanism of the regulation of protein function.

Contemporary protein structure is a result of the trade off between the laws of physics and the evolutionary selection. The polymer nature of proteins played a decisive role in establishing the basic structural and functional units of soluble proteins. We discuss how these elementary building blocks work in the hierarchy of protein domain structure, co-translational folding, as well as in enzymatic activity and molecular interactions. Next, we consider modulators of the protein function, such as intermolecular interactions, disorder-to-order transitions, and allosteric signaling, acting via interference with the protein's structural dynamics. We also discuss the post-translational modifications, which is a complementary intricate mechanism evolved for regulation of protein functions and interactions. In conclusion, we assess an anticipated contribution of discussed topics to the future advancements in the field.