The structure and dynamics in solution of Cu(I) pseudoazurin from Paracoccus pantotrophus

The solution structure and backbone dynamics of Cu(I) pseudoazurin, a 123 amino acid electron transfer protein from Paracoccus pantotrophus, have been determined using NMR methods. The structure was calculated to high precision, with a backbone RMS deviation for secondary structure elements of 0.35 +/- 0.06 Angstrom, using 1,498 distance and 5.5 torsion angle constraints. The protein has a double-wound Greek-key fold with two Lu-helices toward its C-terminus. similar to that of its oxidized counterpart determined by X-ray crysrallography. Comparison of the Cu(I) solution structure with the X-ray structure of the Cu(II) protein shows only small differences in the positions of some of the secondary structure elements. Order parameters S-2, measured For amide nitrogens, indicate that the backbone of the protein is rigid on the picosecond to nanosecond timescale.