homotetrameric

Homotetrameric is a descriptor used in biochemistry to indicate that a protein forms a functional complex composed of four identical polypeptide chains. In such assemblies, all subunits are identical in sequence and structure, and the four chains come together through noncovalent interactions to create a single quaternary unit.

The quaternary architecture commonly exhibits symmetry, most often cyclic (fourfold, C4) or, less commonly, dihedral arrangements. Subunit interfaces create the catalytic or binding surfaces, and in some proteins each subunit contributes to a single active site while in others each subunit provides an independent site.

Tetramerization can stabilize the folded state, expand regulatory capabilities, and enable allosteric control of activity, so substrate binding in one subunit can influence others.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a classic example of a homotetramer, found across bacteria, plants, and animals. Other homotetrameric enzymes include aldehyde dehydrogenases and certain kinases and dehydrogenases that assemble as four identical subunits.

Determining whether a protein is homotetrameric relies on methods such as size-exclusion chromatography, analytical ultracentrifugation, X-ray crystallography, or cryo-electron microscopy, often complemented by cross-linking and mass spectrometry.