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Structure of an engineered bacterial microcompartment shell protein binding a [4Fe-4S] clusterStructure of an engineered bacterial microcompartment shell protein binding a [4Fe-4S] cluster
Structural highlights
FunctionBMCT1_HALO1 A minor component of the bacterial microcompartment (BMC) shell. Expression of 5 proteins in E.coli (BMC-H (Hoch_5815), BMC-P (Hoch_5814), and 3 BMC-T (Hoch_5812, Hoch_5816, Hoch_3341)) forms 40 nm artificial BMCs with a molecular mass of 6.5 MDa. This protein does not form stacked pseudohexamers in the BMC. There are 20 BMC-T pseudohexamers per BMC, composed of mixed BMC-T1, BMC-T2 and BMC-T3. The shell facets are 20-30 Angstroms thick, with 1 of BMC-T trimers protruding to the exterior.[1] [2] Publication Abstract from PubMedBacterial 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 bio-nanoreactors 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 A 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. Structure and Function of a Bacterial Microcompartment Shell Protein Engineered to Bind a [4Fe-4S] Cluster.,Aussignargues C, Pandelia ME, Sutter M, Plegaria JS, Zarzycki J, Turmo A, Huang J, Ducat DC, Hegg EL, Gibney BR, Kerfeld CA J Am Chem Soc. 2015 Dec 24. PMID:26704697[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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