BIOL 200 Lecture Notes - Lecture 12: Animal, Protein Folding, Chymotrypsin
Document Summary
Many proteins have a quaternary structure, which consists of several polypeptide chains that associate into an oligomeric molecule. Each polypeptide chain in such a protein is called a subunit. Hemoglobin, for example, consists of two and two subunits. Each of the four chains has an all- globin fold with a heme pocket. domain swapping is a mechanism for forming oligomeric assemblies. In domain swapping, a secondary or tertiary element of a monomeric protein is replaced by the same element of another protein. Domain swapping can range from secondary structure elements to whole structural domains. It also represents a model of evolution for functional adaptation by oligomerisation, e. g. oligomeric enzymes that have their active site at subunit interfaces. Nature is a tinkerer and not an inventor, new sequences are adapted from pre-existing sequences rather than invented. Domains are the common material used by nature to generate new sequences, they can be thought of as genetically mobile units, referred to as "modules".