Three-dimensional domain swapping in homooligomeric proteins and its functional significance.

In the process of oligomeric structure formation through a mechanism of three-dimensional domain swapping, one domain of a monomeric protein is replaced by the same domain from an identical monomer. The swapped "domain" can represent an entire tertiary globular domain or an element of secondary protein structure, such as an alpha-helix or a beta-strand. Different examples of three-dimensional domain swapping are reviewed; the functional importance of this phenomenon and its role in the development of new properties by some proteins in the process of evolution are considered. The contribution of three-dimensional domain swapping to the formation of linear protein polymers and amyloids is discussed.