Pentamers

A pentamer is a molecular complex composed of five subunits. These subunits can be identical, forming a homopentamer, or different, forming a heteropentamer. The arrangement often produces fivefold symmetry, although the exact geometry can vary with the subunit interfaces. The term can refer to the entire complex or to a repeating five-unit subassembly within a larger structure.

In biology and biochemistry, pentamers are found in a range of proteins and complexes. Pentameric ligand-gated ion channels, such as the nicotinic acetylcholine receptor, assemble as five-subunit rings that form a central pore for ion passage. The B subunit of certain AB5 toxins, including cholera toxin, forms a pentamer that binds to host cell receptors. Viral capsids also use pentameric arrangements at fivefold symmetry axes; such components are often called pentons and are key to assembling the icosahedral shell.

In chemistry and materials science, pentamers refer to oligomers composed of five monomer units. This includes pentapeptides (five amino acids linked together) and five-unit carbohydrate oligomers. Synthetic pentamers and pentameric macrocycles are studied in supramolecular chemistry for their defined geometry and potential applications in nanomaterials, catalysis, and molecular recognition.

Structural characterization of pentameric assemblies typically employs X-ray crystallography or cryo-electron microscopy. The study of pentamers spans multiple disciplines, reflecting how a common five-subunit organization can underpin diverse functions—from signaling and binding to structural packaging and material design.