PROSITE documentation PDOC51933

EutK-Ctail domain profile

Bacterial microcompartments (BMCs) are large proteinaceous structures comprised of a roughly icosahedral shell and a series of encapsulated enzymes. They function as organelles by sequestering particular metabolic processes within the cell. A shell or capsid, which is composed of a few thousand protein subunits, surrounds a series of sequentially acting enzymes and controls the diffusion of substrates and products (including toxic or volatile intermediates) into and out of the lumen. One BMC, which is dedicated to ethanolamine utilization (Eut), is present in several bacteria, including Salmonella enterica and Escherichia coli. The cellular function of the Eut microcompartment is to metabolize ethanolamine without allowing the release of acetaldehyde into the cytosol, thus mitigating the potentially toxic effects of excess aldehyde in the bacterial cytosol and also preventing the volatile acetaldehyde from diffusing across the cell membrane and leading to a loss of carbon. The shells of BMCs are made primarily of a family of proteins whose structural core is the BMC domain (see <PDOC00876>). Four homologous proteins (EutS, EutL, EutK, and EutM) are thought to be the major shell constituents of a functionally complex Eut microcompartment. A fifth protein, EutN is a minor shell component but not homologous to the BMC shell proteins (see <PDOC51932>) [1].

The EutK shell protein is distinct among the shell proteins in the Eut microcompartment. First, although all other BMC proteins studied to date form hexamers (or pseudohexamers, like EutL), EutK is a monomer in solution. The apparent inability of EutK to assemble into a hexamer by itself suggests that different BMC paralogs might form mixed hexamers during assembly of the shell. Second, EutK has an extra protein domain (EutK-Ctail) of about 60 amino acids following the conserved BMC domain. The EutK-Ctail domain is a helix-turn-helix domain (see <PDB:3I71>) that might bind nucleic acids [1].

The profile we developed covers the entire EutK-Ctail domain.