BMCdomain

BMCdomain, short for Bacterial Microcompartment domain, is a conserved protein domain found in a subset of bacterial shell proteins that assemble into bacterial microcompartments (BMCs). These compartments encapsulate specific metabolic pathways, enabling confinement of reactive intermediates and enhanced metabolic efficiency. The BMCdomain is commonly associated with shell components of systems such as the propanediol utilization (Pdu) and ethanolamine utilization (Eut) operons.

Structural and functional characteristics are typical of small, modular domains. The BMCdomain is generally a compact unit, around a hundred amino acids in length, that mediates protein–protein interactions responsible for oligomerization. Through self-association, BMCdomain-containing proteins form hexameric units and larger tessellated assemblies that create the polyhedral shell surrounding the enzymatic core of the microcompartment. The resulting shell provides a selective barrier, where pore-forming loops and regions influence diffusion of substrates and products into and out of the compartment.

Genomic context and diversity are notable features. BMCdomain proteins are encoded within operons alongside encapsulated enzymes, reflecting their role in shell construction and organelle assembly. Variants of the BMCdomain exist, contributing to differences in shell architecture and permeability that suit specific metabolic pathways. Some BMCdomain-containing proteins act primarily as structural components, while others contribute to pore formation and metabolite regulation.

Research and applications. Structural biology studies, including X-ray crystallography and cryo-electron microscopy, have revealed how BMCdomain-containing shell proteins assemble into protective shells. In synthetic biology, BMC-domain–based shells are explored as platforms to engineer compartmentalized reactions and to improve the spatial organization of metabolic pathways.