Bacterial Microcompartment (BMC) domain is a protein domain found in a variety of shell proteins, including CsoS1A, CsoS1B and CsoS1C of Thiobacillus neapolitanus (Halothiobacillus neapolitanus) and their orthologs

Homology (biology)

Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 from other bacteria. These shell proteins form the polyhedral

Polyhedron

In elementary geometry a polyhedron is a geometric solid in three dimensions with flat faces and straight edges...

 structure of organelle

Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....

 that play a metabolic role in bacteria. BMC domain consists of about 90 amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

residues, characterized by β-α-β motif connected by a β-hairpin.

Majority of the shell proteins consist of a single BMC domain in each subunit, forming a hexameric structure that assemble to form the flat facets of the polyhedral shell. To date, two shell proteins were found to consist a tandem BMC domains, of which forms a trimeric structure, giving a pseudo-hexameric appearance.