title: Spectroscopic characterization of a green copper site in a single-domain cupredoxin.
abstract: Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded β-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought.
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Roger
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Biaso
authors.affiliation: Department of Earth and Planetary Science, University of California, Berkeley, California, United States of America.
authors.forename: Cindy J
authors.initials: CJ
authors.lastname: Castelle
authors.affiliation: Unité de Fermentation, Institut de Microbiologie de la Méditerranée, CNRS-FR 3479, Aix Marseille Université, Marseille, France.
authors.forename: Marielle
authors.initials: M
authors.lastname: Bauzan
authors.affiliation: Unité Chimie Physique, Prévention des Risques et Nuisances Technologiques, Faculté de Pharmacie, CNRS-UMR 7263, Aix-Marseille Université, Marseille, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Chaspoul
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Lojou
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Sciara
authors.affiliation: Unité de Biologie Végétale et Microbiologie Environnementales, CNRS-UMR 7265, CEA, Aix Marseille Université, Marseille, France.
authors.forename: Stefano
authors.initials: S
authors.lastname: Caffarri
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Marie-Thérèse
authors.initials: MT
authors.lastname: Giudici-Orticoni
authors.affiliation: Unité de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, CNRS-UMR7281, Aix-Marseille Université, Marseille, France.
authors.forename: Marianne
authors.initials: M
authors.lastname: Ilbert
mesh_terms: D042763:Acidithiobacillus / Q000235:genetics / Q000378:metabolism*; D001400:Azurin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002942:Circular Dichroism; D019295:Computational Biology / Q000379:methods; D003300:Copper / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D017433:Protein Structure, Secondary
chemical_list: D001426:Bacterial Proteins; C050107:cupredoxin; D001400:Azurin; D003300:Copper