Quaternary structure or Quaternary level of protein structural organization, is the structure that results of the assembly of several polypeptide to make an unique functional protein, stabilized through several noncovalent interactions between the R side chain of amino acids from different peptide chains.
The non covalent interactions that maintain this structure are the same non covalent interactions that maintain the tertiary structure: Hydrogen bonds, Ionic interactions, Hydrophobic attractions and Van der Waals Forces.
Based on the definition we gave above, not all proteins show a quaternary level of organization. For having a quaternary structure:
a) The protein should be formed by more than one peptide chain.
b) These chains can not be attached by covalent bonds among them.
Some examples for clarifying the concept:
Myoglobin is formed by a single peptide chain and a hem group. Since Myoglobin is formed by just…
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