Different muscles need different proteins

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Proteins: structure and function

Although all proteins consist of the same building blocks, the amino acids, they have very different biochemical properties and also perform different functions in the organism. Using a few selected examples, the following chapter demonstrates how evolution has solved certain problems and how the amino acid sequence determines the structure and function of a protein.

Example 1: movement

The movement of eukaryotic cells (muscles, cilia, cytoplasmic currents) and the flagella stroke in prokaryotes are based on different principles of movement. The eukaryotic actomyosin and the prokaryotic dynein are not related and are therefore an example of two solutions to the problem of locomotion.

Example 2: oxygen transport

In most animal groups, the oxygen transport is mediated by hemoglobin or myoglobin, both molecules in which oxygen is coordinatively bound to a heme group in the protein. Oxygen transport molecules are highly conserved and hardly differ between groups of organisms - an indication that this invention has only existed once in evolution.

Example 3: Structural components in the organism

Structure-forming proteins take on very specific functions in hair, wool and silk. Collagen fibers stabilize the skin and joints or ensure the flexibility of tendons. Here it is less the tertiary structure than the primary and secondary structure that determine the properties of the respective structural protein.

Example 4: Membrane proteins and their special properties

Membrane proteins do not occur in an aqueous environment. The amino acid composition of membrane proteins, their properties and their function in the organism is therefore very different from that of cytoplasmic proteins.

Example 5: Proteins that require prosthetic groups for their function

Proteins that carry sugar, lipids or, for example, heme groups, take on a variety of tasks in the organism. In addition to the above-mentioned oxygen transport, which is mediated by a heme protein, many respiratory processes are linked to proteins that need metals such as iron or molybdenum (cytochrome, nitrogenase) or, as in the case of flavoproteins, FMN or FAD Have cofactors. Without the non-protein part, these proteins would not be able to fulfill their function.