Question

The major reason behind some proteins having quaternary structure is

• A. To enable them to respond to environmental changes in a more complex way than monomeric proteins.
• B. To assemble the monomers to form a coordinated polymeric structure.
• C. In the case of enzymes, to improve their rate of catalysis.
• D. None of the above

Answer 1

The correct option is B To assemble the monomers to form a coordinated polymeric structure.

In proteins, Quarternary structure is present in the case of multimeric or oligomeric proteins. It is homogenous if the polypeptide is similar or heterogeneous if the polypeptides are different. Here (in the quarternary structure) the different polypeptide chains interact and get oriented with respect to each other in a specific manner. Some enzymes are multimeric proteins with different protein chains interacting in a particular fashion in three-dimensional space to give rise to active sites, crevices, pockets and other structures on the surface to form the functional protein molecule which can act as a catalyst.
Also in the multimeric proteins, the binding sites are derived by different protein chains. Only those proteins made of two or more polypeptide chains have a quaternary structure. Insulin (two chains), haemoglobin (four chains) and immunoglobulins (antibodies, four chains) are some examples of protein having a quaternary structure.