title: In Vitro Characterization and Concerted Function of Three Core Enzymes of a Glycyl Radical Enzyme - Associated Bacterial Microcompartment.
abstract: Many bacteria encode proteinaceous bacterial microcompartments (BMCs) that encapsulate sequential enzymatic reactions of diverse metabolic pathways. Well-characterized BMCs include carboxysomes for CO2-fixation, and propanediol- and ethanolamine-utilizing microcompartments that contain B12-dependent enzymes. Genes required to form BMCs are typically organized in gene clusters, which promoted their distribution across phyla by horizontal gene transfer. Recently, BMCs associated with glycyl radical enzymes (GREs) were discovered; these are widespread and comprise at least three functionally distinct types. Previously, we predicted one type of these GRE-associated microcompartments (GRMs) represents a B12-independent propanediol-utilizing BMC. Here we functionally and structurally characterize enzymes of the GRM of Rhodopseudomonas palustris BisB18 and demonstrate their concerted function in vitro. The GRM signature enzyme, the GRE, is a dedicated 1,2-propanediol dehydratase with a new type of intramolecular encapsulation peptide. It forms a complex with its activating enzyme and, in conjunction with an aldehyde dehydrogenase, converts 1,2-propanediol to propionyl-CoA. Notably, homologous GRMs are also encoded in pathogenic Escherichia coli strains. Our high-resolution crystal structures of the aldehyde dehydrogenase lead to a revised reaction mechanism. The successful in vitro reconstitution of a part of the GRM metabolism provides insights into the metabolic function and steps in the assembly of this BMC.
authors.affiliation: Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, D-35043, Marburg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Zarzycki
authors.affiliation: MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
authors.forename: Markus
authors.initials: M
authors.lastname: Sutter
authors.affiliation: Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, D-35043, Marburg, Germany.
authors.forename: Niña Socorro
authors.initials: NS
authors.lastname: Cortina
authors.affiliation: Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, D-35043, Marburg, Germany.
authors.forename: Tobias J
authors.initials: TJ
authors.lastname: Erb
authors.affiliation: MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA.|Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.|Department of Biochemistry &Molecular Biology, Michigan State University, 603 Wilson Road, East Lansing, MI 48824, USA.|Berkeley Synthetic Biology Institute, Berkeley, CA, USA.|Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, USA.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Kerfeld
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002451:Cell Compartmentation; D011408:Propanediol Dehydratase / Q000737:chemistry* / Q000378:metabolism; D019946:Propylene Glycol / Q000378:metabolism; D011485:Protein Binding; D012241:Rhodopseudomonas / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D019946:Propylene Glycol; D000444:Aldehyde Dehydrogenase; D011408:Propanediol Dehydratase