pentameric

Pentameric describes a structure or assembly composed of five subunits or parts. It derives from the Greek penta- meaning five and meros meaning part. The term is used in chemistry, biochemistry, and virology to describe the stoichiometry and arrangement of complexes. A five-subunit assembly is called a pentamer, and pentameric refers to its five-subunit organization, which may involve identical or different subunits.

In chemistry and materials science, pentameric arrangements appear in small molecules, coordination complexes, and supramolecular systems that form rings or capsules with five components. The symmetry is typically C5 or D5, which influences shape, stability, and interactions with other molecules or surfaces.

In biology, pentameric protein complexes are common. A prominent example is pentameric ligand-gated ion channels (pLGICs), including nicotinic acetylcholine receptors, GABA_A receptors, and glycine receptors, which assemble from five subunits around a central pore to regulate ion flow in response to neurotransmitters. Subunit composition and arrangement affect pharmacology and gating properties.

Structural considerations include fivefold symmetry and potential heteromeric compositions. While many pentameric proteins display strict pentameric symmetry, some arrangements are quasi-symmetric or dynamic, with subunits capable of exchanging or moving during function.

In virology, certain viral capsids use pentameric components at their vertices; in icosahedral viruses, pentameric capsomers (pentons) contribute to the shell’s geometry.

Etymology: from Greek pente "five" and meros "part."