Tertiary structure of proteins

Tertiary structure of myoglobin

The tertiary structure of proteins is formed on the arrangement of the secondary structure of a polypeptide when it folds in on itself, originating a globular conformation, which remains stable due to the existence of links between the R radicals of amino acids. Between these bonds appear disulfide bridges between amino acid radicals that have sulfur (cysteine) and other hydrophobic forces.

The two possible tertiary structures are the globular structure and the fibrillar structure. The globular structure is "ball" shaped, soluble, and is typical of hormones or enzymes. The fibrous structure is characterized by giving the protein the shape of a filament and being insoluble; examples of proteins with this structure are alpha or beta-keratin and collagen.

The tertiary structure of a protein is the three-dimensional distribution of all the atoms that make up the protein. It can be affirmed that the biological properties of these derive from the tertiary structure, since the arrangement in space of the different functional groups of the protein determines its ability to interact with other groups and ligands. In this way, the primary structure (amino acid sequence) of the protein determines the tertiary structure.

Schematic representation in diagram of tapes de la Triosa fosfato isomerasa, drawn by Jane Richardson.

The tertiary structure of a protein is generally made up of several sections with different secondary structures.
Regarding the levels of the protein structure, in the tertiary structure generally the nonpolar amino acids are located towards the interior of the protein and the polar ones towards the exterior, so that they can interact with water surrounding. In the case of integral membrane proteins, the hydrophobic amino acids are exposed within the lipid bilayer. Therefore, this type of structure is what gives proteins their physicochemical particularities, such as the polarity or apolarity of the molecule.

Forces that stabilize the tertiary structure

The tertiary structure of proteins is supported by four classes of interactions: disulfide bonds between Cys, hydrogen bonds between side chains, ionic interactions, van der Waals interactions, and the hydrophobic effect (exclusion of water molecules). avoiding their contact with the hydrophobic residues, which remain packed inside the structure) and, recently, as a consequence of research in molecular anatomy, a close relationship between the interactions between the hydrophobic regions of the aliphatic chains has been discovered. protein radicals. Interactions between the side chains of protein residues direct the polypeptide to form a compact structure...