title: Sco proteins are involved in electron transfer processes.
abstract: Sco proteins are widespread in eukaryotic and in many prokaryotic organisms. They have a thioredoxin-like fold and bind a single copper(I) or copper(II) ion through a CXXXC motif and a conserved His ligand, with both tight and weak affinities. They have been implicated in the assembly of the Cu(A) site of cytochrome c oxidase as copper chaperones and/or thioredoxins. In this work we have structurally characterized a Sco domain which is naturally fused with a typical electron transfer molecule, i.e., cytochrome c, in Pseudomonas putida. The thioredoxin-like Sco domain does not bind copper(II), binds copper(I) with weak affinity without involving the conserved His, and has redox properties consisting of a thioredoxin activity and of the ability of reducing copper(II) to copper(I), and iron(III) to iron(II) of the cytochrome c domain. These findings indicate that the His ligand coordination is the discriminating factor for introducing a metallochaperone function in a thioredoxin-like fold, typically responsible for electron transfer processes. A comparative structural analysis of the Sco domain from P. putida versus eukaryotic Sco proteins revealed structural determinants affecting the formation of a tight-affinity versus a weak-affinity copper binding site in Sco proteins.
authors.affiliation: Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Banci
authors.forename: Ivano
authors.initials: I
authors.lastname: Bertini
authors.forename: Simone
authors.initials: S
authors.lastname: Ciofi-Baffoni
authors.forename: Tatiana
authors.initials: T
authors.lastname: Kozyreva
authors.forename: Mirko
authors.initials: M
authors.lastname: Mori
authors.forename: Shenlin
authors.initials: S
authors.lastname: Wang
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D045304:Cytochromes c