Crystal structure of auracyanin, a "blue" copper protein from the green thermophilic photosynthetic bacterium Chloroflexus aurantiacus

Department of Chemistry and Biochemistry, Arizona State University, Phoenix, Arizona, United States
Journal of Molecular Biology (Impact Factor: 4.33). 03/2001; 306(1):47-67. DOI: 10.1006/jmbi.2000.4201
Source: PubMed


Auracyanin B, one of two similar blue copper proteins produced by the thermophilic green non-sulfur photosynthetic bacterium Chloroflexus aurantiacus, crystallizes in space group P6(4)22 (a=b=115.7 A, c=54.6 A). The structure was solved using multiple wavelength anomalous dispersion data recorded about the CuK absorption edge, and was refined at 1.55 A resolution. The molecular model comprises 139 amino acid residues, one Cu, 247 H(2)O molecules, one Cl(-) and two SO(4)(2-). The final residual and estimated standard uncertainties are R=0.198, ESU=0.076 A for atomic coordinates and ESU=0.05 A for Cu---ligand bond lengths, respectively. The auracyanin B molecule has a standard cupredoxin fold. With the exception of an additional N-terminal strand, the molecule is very similar to that of the bacterial cupredoxin, azurin. As in other cupredoxins, one of the Cu ligands lies on strand 4 of the polypeptide, and the other three lie along a large loop between strands 7 and 8. The Cu site geometry is discussed with reference to the amino acid spacing between the latter three ligands. The crystallographically characterized Cu-binding domain of auracyanin B is probably tethered to the periplasmic side of the cytoplasmic membrane by an N-terminal tail that exhibits significant sequence identity with known tethers in several other membrane-associated electron-transfer proteins.

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    • "The type I blue copper protein auracyanin, which has a single copper atom coordinated by two histidine, one cysteine and one methionine residues at the active site, is proposed to participate in the electron transfer from ACIII to the reaction center in Cfl. aurantiacus [35,47-49], and it has also been recently characterized in Roseiflexus castenholzii [50]. Additionally, an auracyanin gene (trd_0373) has been identified in the genome of the non-photosynthetic bacterium Thermomicrobium roseum DSM 5159, which is evolutionally related to Cfl. aurantiacus [51]. "
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