title: Selective molecular transport through the protein shell of a bacterial microcompartment organelle.
abstract: Bacterial microcompartments are widespread prokaryotic organelles that have important and diverse roles ranging from carbon fixation to enteric pathogenesis. Current models for microcompartment function propose that their outer protein shell is selectively permeable to small molecules, but whether a protein shell can mediate selective permeability and how this occurs are unresolved questions. Here, biochemical and physiological studies of structure-guided mutants are used to show that the hexameric PduA shell protein of the 1,2-propanediol utilization (Pdu) microcompartment forms a selectively permeable pore tailored for the influx of 1,2-propanediol (the substrate of the Pdu microcompartment) while restricting the efflux of propionaldehyde, a toxic intermediate of 1,2-propanediol catabolism. Crystal structures of various PduA mutants provide a foundation for interpreting the observed biochemical and phenotypic data in terms of molecular diffusion across the shell. Overall, these studies provide a basis for understanding a class of selectively permeable channels formed by nonmembrane proteins.
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011;
authors.forename: Chiranjit
authors.initials: C
authors.lastname: Chowdhury
authors.affiliation: Molecular Biology Institute.
authors.forename: Sunny
authors.initials: S
authors.lastname: Chun
authors.affiliation: UCLA-DOE Institute for Genomics and Proteomics, and.
authors.forename: Allan
authors.initials: A
authors.lastname: Pang
authors.affiliation: UCLA-DOE Institute for Genomics and Proteomics, and.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sawaya
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011;
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Sinha
authors.affiliation: Molecular Biology Institute, UCLA-DOE Institute for Genomics and Proteomics, and Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095 bobik@iastate.edu yeates@mbi.ucla.edu.
authors.forename: Todd O
authors.initials: TO
authors.lastname: Yeates
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011; bobik@iastate.edu yeates@mbi.ucla.edu.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Bobik
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D015388:Organelles / Q000378:metabolism*; D019946:Propylene Glycol / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D019946:Propylene Glycol; D005990:Glycerol
keywords: B12; Salmonella; carboxysome; microcompartment; protein channel