homomultimer

Homomultimer refers to a protein complex formed by multiple identical subunits, each encoded by the same gene and sharing the same amino acid sequence. This is a subset of oligomeric proteins and is contrasted with heteromultimers, which consist of different subunits.

Subunits assemble into defined oligomeric states, such as dimers, trimers, tetramers, and larger assemblies. The arrangement is often symmetric, with cyclic (Cn) or dihedral (Dn) symmetry, and interfaces between subunits create the functional sites of the complex. Assembly can be driven by noncovalent interactions and may occur co-translationally or after synthesis.

Homomultimers can enhance stability, cooperativity, and regulation. Many enzymes and binding proteins function as homomultimers, and in some cases the quaternary structure enables allosteric communication between subunits.

Examples include ferritin, which in some forms is a 24-subunit homopolymer; GroEL, a 14-subunit chaperonin with identical subunits; and certain transcription factors like p53, which forms a homotetramer. The term is used broadly in biochemistry and structural biology to categorize complexes by subunit identity rather than subunit type.

Techniques used to study homomultimers include X-ray crystallography, cryo-electron microscopy, small-angle X-ray scattering, analytical ultracentrifugation, and various forms of mass spectrometry and cross-linking.