Encapsulin

Encapsulin is a family of protein-based nanocompartments found in bacteria and archaea. These shells self-assemble from a single type of capsid protein into polyhedral structures, typically icosahedral, with diameters in the tens of nanometers. Inside the shell, one or more cargo proteins are encapsulated. Cargo proteins often carry short targeting peptides that mediate their capture by the interior surface of the shell. Common cargo types include ferritin-like proteins involved in mineral storage or detoxification, as well as various oxidoreductases and other enzymes tied to metabolism or stress responses.

Encapsulins provide a confined microenvironment that can isolate reactive chemistry, protect cellular components from harmful intermediates, and concentrate enzymes to improve catalytic efficiency. In many systems, encapsulation is linked to iron handling, detoxification of reactive oxygen species, and maintenance of redox balance. The genes encoding encapsulins typically form operons that include the capsid gene and one or more cargo genes, and these operons are found across diverse bacterial and some archaeal lineages.

Biogenesis involves spontaneous self-assembly of the capsid proteins, often coordinated with cellular growth or stress responses. Cargo delivery is mediated by interactions between targeting peptides and the interior surface of the shell, allowing selective sequestration of enzymes inside the compartments.

Applications in biotechnology and nanotechnology are an active area of research. Encapsulins are explored as modular scaffolds for creating nanoreactors, co-localizing enzymes to enhance pathways, and developing cargo delivery systems. The modularity and relative stability of encapsulin shells make them attractive platforms for synthetic biology and materials science.