dodecamers

A dodecamer is a molecular complex composed of twelve subunits, or monomers. In biochemistry, the term is used for protein assemblies, nucleic acid–protein complexes, or other macromolecular constructs that contain twelve units. Dodecamers can be homododecamers, with all subunits identical, or heterododecamers, containing two or more different subunit types.

Structure and assembly: Dodecamers often exhibit high symmetry, commonly forming two stacked hexameric rings or a single cyclic arrangement, though exact symmetry varies. Subunit–subunit interfaces drive self-assembly and can be influenced by factors such as pH, ionic strength, metal cofactors, or ligand binding. They may be stable particles or dynamic assemblies that can exchange subunits under certain conditions.

Functions: In biology, dodecameric assemblies serve a range of roles. They can act as protective cages, enzymes, or storage modules, and in some viruses, dodecameric capsid components contribute to shell formation. A well-known example is the Dps protein, which forms a dodecameric shell to package and protect DNA in bacteria under stress. In other contexts, protein cages provide nanoscale containers for catalysis or drug delivery.

Examples: Dps proteins commonly form dodecamers; other proteins may assemble into dodecamers in response to stress or during the assembly of larger complexes. The ferritin family forms 24-subunit assemblies rather than dodecamers, illustrating that oligomeric symmetry varies across related proteins.

See also: oligomer, multimer, decamer, icosamer, protein cage.