Quaternary protein structure refers to the spatial arrangement or organization of multiple protein subunits that interact with each other to form a functional and stable complex. It represents the higher-level structure beyond the primary, secondary, and tertiary structures of a protein.
In quaternary structure, two or more individual protein subunits, known as multimers, come together to form a larger complex. These subunits can be identical (homomultimers) or different (heteromultimers). The association of these subunits is primarily driven by non-covalent interactions, such as hydrogen bonds, ionic interactions, hydrophobic interactions, and van der Waals forces.
The formation of quaternary structure is crucial for many proteins to fulfill their biological functions. It enhances protein stability, provides functional advantages, and allows for the regulation of protein activity. The complex may generate new binding sites or allosteric sites, altering the protein's activity or specificity. Additionally, quaternary structure can influence protein localization, cellular assembly, and signaling pathways.
Quaternary structure is often essential for proteins involved in key biological processes, such as enzyme catalysis, transport across cellular membranes, signal transduction, DNA replication, and many others. Examples of proteins with quaternary structure include hemoglobin, which consists of four subunits, and DNA polymerase, which typically forms a multimeric complex.
Overall, the study of quaternary protein structures provides valuable insights into the mechanisms underlying protein function, regulation, and cellular processes.
