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4.4.1.3. Tertiary structure of proteins

Tertiary structure of proteins

The tertiary structure is the arrangement that the secondary structure adopts in space. Therefore, the primary structure determines which is the secondary and the tertiary structure.

This structure is maintained thanks to the bonds that occur between the -R radicals of the different amino acids , located at positions very far from the peptide chain.

  • Hydrogen bridge bonds between nonionic polar groups in which there are partial charges in their side chain.
  • Electrostatic attractionsionic bonds between R groups of acidic amino acids (negatively charged, -COO-) and basic amino acids (positively charged, -NH3+).
  • Hydrophobic attractions and Van der Waals forces between aliphatic radicals of apolar amino acid side chains.
  • Disulfide bridges, covalent bonds between two thiol groups (-SH), corresponding to two cysteines .

If one amino acid is substituted for another (primary structure), the three-dimensional structure of the protein will be altered, since none of these bonds will be formed. The spatial arrangement of the different functional groups determines their interaction with other molecules, so this structure is directly responsible for the biological properties of a protein .

The tertiary structure is the highest structural level that proteins made up of a single polypeptide chain can have.

It is frequent that spatial combinations of the α-helix or β- sheet type are repeated, called structural domains, which have a very specific geometry that allows them to perform very important functions within the protein, such as the active center of enzymes .

In general, there are two types of tertiary structures in proteins:

Fundamental ideas about the tertiary structure of proteins

The  tertiary structure  is the arrangement that the secondary structure adopts  in space by the bonds that occur between the -R radicals of the different  amino acids, located at positions very far from the peptide chain.

  • Hydrogen bridge bonds.
  • Electrostatic attractions,  ionic bonds  between R groups of acidic amino acids (negatively charged, -COO- ) and basic amino acids (positively charged, -NH3+).
  • Hydrophobic attractions and Van der Waals forces .
  • Disulfide bridges.

The tertiary structure can be of two forms: