Steve Ealick's Research Group
PDB file: 1RCY
Cupredoxins (type-1 copper-containing proteins) are involved in electron transport in plants and bacteria. They have a strong spectroscopic absorbance at 600 nm, yielding a characteristic blue color in the reduced state. This reflects a covalent linkage betweeen cysteinyl sulfur and copper. The X-ray crystal structure of the oxidized form of the extremely stable and highly oxidizing cupredoxin rusticyanin from Thiobacillus ferrooxidans has been determined by the method of multiwavelength anomalous diffraction (MAD) and refined to 1.9 Å resolution. Rusticyanin is a copper-containing metalloprotein, which is composed of a core b-sandwich fold. In rusticyanin the β-sandwich is composed of a six- and a seven-stranded β-sheet. Also like other cupredoxins, the copper ion is coordinated by a cluster of four conserved residues (His 85, Cys138, His143, Met148) arranged in a distorted tetrahedron.
The rusticyanin copper binding site shows the copper, the liganding residues and the supporting secondary structural elements. The Type II β-turn and the 310 helix may represent a region of structural rigidity that helps define and support the distorted coordination geometry.
Walter RL, Ealick SE, Friedman AM, Blake II RC, Proctor P, and Shoham M. Multiple Wavelength Anomalous Diffraction (MAD) Crystal Structure of Rusticyanin: A Highly Oxidizing Cupredoxin with Extreme Acid Stability. J. Mol. Biol. 263:730-751 (1996).