what are Quaternary structure of protein?
Quaternary structure , 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.
The arrangement of the monomers in the three-dimensional protein is the quaternary structure. The most common example used to illustrate quaternary structure is the hemoglobin protein.