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Structural and mechanistic insights into an extracytoplasmic copper trafficking pathway in Streptomyces lividans

DOI: 10.1042/BJ20140017 DOI Help
PMID: 24548299 PMID Help

Authors: Mike Hough (University of Essex) , Katie Blundell (University of Essex) , Jonathan Worrall (University of Essex) , Erik Vijgenboom (University of Essex)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: February 2014
Diamond Proposal Number(s): 7641

Abstract: In Streptomyces lividans an extracytoplasmic copper-binding Sco protein plays a role in two unlinked processes: (i) initiating a morphological development switch and (ii) facilitating the co-factoring of the CuA domain of CcO (cytochrome c oxidase). How Sco obtains copper once secreted to the extracytoplasmic environment is unknown. In the present paper we report on a protein possessing an HX6MX21HXM motif that binds a single cuprous ion with subfemtomolar affinity. High-resolution X-ray structures of this extracytoplasmic copper chaperone-like protein (ECuC) in the apo- and Cu(I)-bound states reveal that the latter possesses a surface-accessible cuprous-ion-binding site located in a dish-shaped region of ?-sheet structure. A cuprous ion is transferred under a favourable thermodynamic gradient from ECuC to Sco with no back transfer occurring. The ionization properties of the cysteine residues in the Cys86xxxCys90 copper-binding motif of Sco, together with their positional locations identified from an X-ray structure of Sco, suggests a role for Cys86 in initiating an inter-complex ligand-exchange reaction with Cu(I)–ECuC. Generation of the genetic knockouts, ?sco, ?ecuc and ?sco/ecuc, and subsequent in vivo assays lend support to the existence of a branched extracytoplasmic copper-trafficking pathway in S. lividans. One branch requires both Sco and to a certain extent ECuC to cofactor the CuA domain, whereas the other uses only Sco to deliver copper to a cuproenzyme to initiate morphological development.

Journal Keywords: Amino; Apoproteins; Bacterial; Biological; Carrier; Copper; Crystallography; X-Ray; Cysteine; Electron; Gene; Kinetics; Membrane; Metallochaperones; Models; Molecular; Mutant; Protein; Tertiary; Recombinant; Sequence; Streptomyces lividans

Subject Areas: Biology and Bio-materials, Medicine

Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography

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