proteindringer

Proteindringer is a Danish term that can refer to ring-shaped protein assemblies, i.e., protein complexes that adopt a circular, torus-like geometry. The term is not tightly standardized and may be used to describe both naturally occurring rings and synthetically engineered protein rings.

In nature, several protein complexes form ring-like structures. Examples include the chaperonin GroEL/GroES, which forms two stacked rings that enclose substrate proteins, and the alpha ring of the 20S proteasome, which assembles into an annular gate. Other proteins polymerize into circular rings involved in cell division, such as FtsZ, which can assemble into a ring at the division site. There are also smaller toroidal rings formed by bacterial and viral proteins that encapsulate nucleic acids or other cargo.

Structural features vary, but many proteindringer display symmetry with six to twelve subunits per ring. Some rings stack to create larger cylinders or cages, while others remain single-layered. Formation generally occurs by self-assembly driven by subunit–subunit interactions, sometimes aided by chaperones or cofactors. In engineered systems, researchers use circularly permuted proteins, designed linkers, and interface redesign to create new rings with specified sizes and internal cavities.

Functions of proteindringer include acting as gates or pores, scaffolds for assembling other molecules, and containers for encapsulating enzymes or drugs. In biotechnology, ring-shaped proteins are explored as nanoscale reactors, delivery vehicles, and components of synthetic molecular machines.

See also: protein complex, chaperonin, proteasome, FtsZ, ferritin, self-assembly, nanotechnology.