The concept of quaternary structure was first put forward by Bernal in 1958. Quaternay structure is defined as the level of form in which units of tertiary structure aggregate to form homo or hetero-multimers. Quaternary structure is the interaction of non-covalently bound monomeric protein subunits to form oligomers. Such complexes are involved in various biological processes, including metabolism, signal transduction and chromosome replicating etc.
The protein quaternay structure file Server (PQS) is a internet resource that makes available coordinates for probable quaternay states for structures contained in the Protein Data Bank (PDb) that were determined by X-ray crystallography.
Uses of the PQS server
1.Gives complete description of domain structures that involve more than one chain.
2.Residues that are buried at protein protein interface can be conserved and this information can be used in homology model building to improve alignment.
website: http://pqs.ebi.ac.uk/
