title: Metalloproteins diversified: the auracyanins are a family of cupredoxins that stretch the spectral and redox limits of blue copper proteins.
abstract: The metal sites of electron transfer proteins are tuned for function. The type 1 copper site is one of the most utilized metal sites in electron transfer reactions. This site can be tuned by the protein environment from +80 mV to +680 mV in typical type 1 sites. Accompanying this huge variation in midpoint potentials are large changes in electronic structure, resulting in proteins that are blue, green, or even red. Here, we report a family of blue copper proteins, the auracyanins, from the filamentous anoxygenic phototroph Chloroflexus aurantiacus that display the entire known spectral and redox variations known in the type 1 copper site. C. aurantiacus encodes four auracyanins, labeled A-D. The midpoint potentials vary from +83 mV (auracyanin D) to +423 mV (auracyanin C). The electronic structures vary from classical blue copper UV-vis absorption spectra (auracyanin B) to highly perturbed spectra (auracyanins C and D). The spectrum of auracyanin C is temperature-dependent. The expansion and divergent nature of the auracyanins is a previously unseen phenomenon.
authors.affiliation: Graduate Program in Plant Biology, Departments of ‡Biology and §Chemistry, and ⊥Photosynthetic Antenna Research Center (PARC), Washington University in St. Louis , St. Louis, Missouri 63130, United States.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: King
authors.forename: Chelsea L
authors.initials: CL
authors.lastname: McIntosh
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Halsey
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Lada
authors.forename: Dariusz M
authors.initials: DM
authors.lastname: Niedzwiedzki
authors.forename: Jason W
authors.initials: JW
authors.lastname: Cooley
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D000595:Amino Acid Sequence; D001400:Azurin; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D041861:Chloroflexus / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004579:Electron Transport; D055724:Electrophysiological Phenomena; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D016415:Sequence Alignment; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; C073756:auracyanin A protein, bacteria; C050107:cupredoxin; D001400:Azurin; D003300:Copper