Oligomerization of cytochrome c, myoglobin, and related heme proteins by 3D domain swapping

Oligomerization of heme proteins is useful for construction of new materials with cooperative and systematic functions; thus, diverse methods have been applied for construction of artificial heme protein oligomers. Three-dimensional (3D) domain swapping is a protein oligomerization phenomenon that exchanges the same domain or secondary structural element between molecules. 3D domain swapping was first reported in 1994; since then many proteins have been reported to domain swap. Our research group has been showing that various heme proteins domain swap. We also found that domain swapping of heme proteins occurs at the early stage of protein folding, and utilized it to construct various heme protein assemblies, including nanorings, cages, hetero dimers with different active sites, and a ligand-binding reversible monomer-polymer system. In this review, the basics and applications of domain swapping of heme proteins are summarized.