Conformational studies of copper proteins. Pseudomonas blue protein and Polyporus laccase.

Optical rotatory dispersion and circular dichroism spectra of the Pseudomonas blue protein and lactase B from Polyporus versicolor are presented from 190 to 700 mp. Circular dichroism spectra of both proteins show six ellipticity bands above 300 rnp associated with the copper chromophore, indicating more transitions to be present in these copper protein complexes than the three parity-forbidden d-d transitions associated with Cu(I1) in its common symmetries. A Gaussian analysis of the visible spectra of these proteins is presented. The same set of bands generates both the absorption and the circular dichroism spectra by the adjustment of the signs and the heights of the bands, while keeping the positions and the band widths constant. Below 1.8 x lo4 cm-l, both proteins show three bands in the circular dichroism spectrum with signs (+, +, -) for the blue protein and (+, -, +) for lactase B. The uniqueness of the analysis has been established by using the KronigKramers transform to generate the optical rotatory dispersion spectrum of the blue protein. Comparisons are made to the circular dichroism spectra of a Cu(I1) complex of known donor atoms and geometry, [Cu(II)(glycyl-I.-valine)]. Each protein creates a unique chemical environment for the aromatic residues. The Pseudomonas blue protein shows at least seven aromatic ellipticity bands, both positive and negative ([e] f6 X lo3 deg cm2 per decimole), whereas lactase B shows three large positive aromatic bands ([0] = 1 to 2.7 X lo4 deg cm2 per decimole). In the region of the absorption bands of the peptide bonds, the blue protein shows a negative ellipticity band at 222 rnp ([e] = 4.9 X lo3 on a mean residue basis) and a positive band at 196 rnp ([0] = 1.28 x lo4 on a mean residue basis). A prominent negative band is not present at 206 mp, and the circular dichroism spectrum exhibits a crossover point at 206 mp. A preliminary analysis based on the computed contours of both the optical rotatory dispersion and circular dichroism spectra