title: Structure of a trimeric bacterial microcompartment shell protein, EtuB, associated with ethanol utilization in Clostridium kluyveri.
abstract: It has been suggested that ethanol metabolism in the strict anaerobe Clostridium kluyveri occurs within a metabolosome, a subcellular proteinaceous bacterial microcompartment. Two bacterial microcompartment shell proteins [EtuA (ethanol utilization shell protein A) and EtuB] are found encoded on the genome clustered with the genes for ethanol utilization. The function of the bacterial microcompartment is to facilitate fermentation by sequestering the enzymes, substrates and intermediates. Recent structural studies of bacterial microcompartment proteins have revealed both hexamers and pentamers that assemble to generate the pseudo-icosahedral bacterial microcompartment shell. Some of these shell proteins have pores on their symmetry axes. Here we report the structure of the trimeric bacterial microcompartment protein EtuB, which has a tandem structural repeat within the subunit and pseudo-hexagonal symmetry. The pores in the EtuB trimer are within the subunits rather than between symmetry related subunits. We suggest that the evolutionary advantage of this is that it releases the pore from the rotational symmetry constraint allowing more precise control of the fluxes of asymmetric molecules, such as ethanol, across the pore. We also model EtuA and demonstrate that the two proteins have the potential to interact to generate the casing for a metabolosome.
authors.affiliation: Centre for Molecular Processing, School of Biosciences, University of Kent, Giles Lane, Canterbury, Kent, UK.
authors.forename: Dana
authors.initials: D
authors.lastname: Heldt
authors.forename: Stefanie
authors.initials: S
authors.lastname: Frank
authors.forename: Arefeh
authors.initials: A
authors.lastname: Seyedarabi
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Ladikis
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Parsons
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Warren
authors.forename: Richard W
authors.initials: RW
authors.lastname: Pickersgill
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D003001:Cloning, Molecular; D047010:Clostridium kluyveri / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D000431:Ethanol / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D055503:Protein Multimerization / Q000502:physiology; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D018272:Porins; D000431:Ethanol