Quaternary Structure Definition:

The structure that arises when a protein consists of two or more folded polypeptide chains that aggregate to form one protein complex.

Quaternary Structure Explained:

Polypeptide chain and are thus called monomeric. Other protein s are composed of two or more polypeptide range called subunit. The quartet organization describes the placement and position of each of the subunits in a multiunit protein. The stabilizing forces that delay the polypeptide subunits together are the same forces that are responsible for tertiary structure stabilization. A major force stabilizing the tetrad structure is the hydrophobic fundamental interaction among nonpolar side chains at the contact regions of the subunits. Additional stabilizing forces include interaction between side chains of the subunits, including electrostatic interactions between Classical Greek groups of opposite direction.