title: Structure and Function of a Bacterial Microcompartment Shell Protein Engineered to Bind a [4Fe-4S] Cluster.
abstract: Bacterial microcompartments (BMCs) are self-assembling organelles composed of a selectively permeable protein shell and encapsulated enzymes. They are considered promising templates for the engineering of designed bionanoreactors for biotechnology. In particular, encapsulation of oxidoreductive reactions requiring electron transfer between the lumen of the BMC and the cytosol relies on the ability to conduct electrons across the shell. We determined the crystal structure of a component protein of a synthetic BMC shell, which informed the rational design of a [4Fe-4S] cluster-binding site in its pore. We also solved the structure of the [4Fe-4S] cluster-bound, engineered protein to 1.8 Å resolution, providing the first structure of a BMC shell protein containing a metal center. The [4Fe-4S] cluster was characterized by optical and EPR spectroscopies; it has a reduction potential of -370 mV vs the standard hydrogen electrode (SHE) and is stable through redox cycling. This remarkable stability may be attributable to the hydrogen-bonding network provided by the main chain of the protein scaffold. The properties of the [4Fe-4S] cluster resemble those in low-potential bacterial ferredoxins, while its ligation to three cysteine residues is reminiscent of enzymes such as aconitase and radical S-adenosymethionine (SAM) enzymes. This engineered shell protein provides the foundation for conferring electron-transfer functionality to BMC shells.
authors.forename: Clément
authors.initials: C
authors.lastname: Aussignargues
authors.affiliation: Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Maria-Eirini
authors.initials: ME
authors.lastname: Pandelia
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Markus
authors.initials: M
authors.lastname: Sutter
authors.forename: Jefferson S
authors.initials: JS
authors.lastname: Plegaria
authors.forename: Jan
authors.initials: J
authors.lastname: Zarzycki
authors.forename: Aiko
authors.initials: A
authors.lastname: Turmo
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Huang
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Ducat
authors.forename: Eric L
authors.initials: EL
authors.lastname: Hegg
authors.affiliation: Department of Chemistry, Brooklyn College , Brooklyn, New York 11210, United States.|Ph.D. Programs in Chemistry and Biochemistry, The Graduate Center of the City University of New York , New York, New York 10016, United States.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Gibney
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Plant and Microbial Biology, University of California , Berkeley, California 94720, United States.|Berkeley Synthetic Biology Institute , Berkeley, California 94720, United States.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Kerfeld
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D011994:Recombinant Proteins; D003545:Cysteine