Encapsulins

Encapsulins are protein-based nanocompartments found in bacteria and archaea. They consist of a self-assembling icosahedral shell formed by many copies of a single encapsulin shell protein. The shells enclose one or more cargo proteins, which are directed to the interior by short targeting peptides attached to the cargo or to the shell.

Shells typically range from about 20 to 40 nanometers in diameter and adopt icosahedral symmetry, creating a closed interior space that concentrates enzymes and substrates while isolating reactive cargo from the cytoplasm.

In cells, encapsulins sequester enzymes and reactive cargo, enabling compartmentalization of biochemical reactions. Cargo often includes ferritin-like iron storage proteins, DyP-type peroxidases, and other oxidoreductases. The encapsulation protects the cell from reactive intermediates, supports specific metabolic processes such as iron storage, oxidative stress management, or detoxification, and can enhance enzyme efficiency by localizing reactions.

Encapsulin gene clusters feature a shell protein gene together with one or more cargo genes, often encoding C-terminal targeting peptides. The system is widespread among bacteria and archaea and is thought to play roles in metabolism and stress responses. The exact functions vary by organism and cargo.

Historically, encapsulins were discovered through genome mining and subsequent structural and functional studies, which revealed their shell architecture and cargo-loading mechanism. Since then, encapsulins have attracted interest as modular nanocompartments for biotechnology, enabling encapsulation of enzymes to create nanoreactors, improve stability, or engineer controlled reaction environments. They also offer potential as programmable nanocontainers for materials science and nanomedicine, though practical applications are in early development.