title: Comparative Cd-113 nuclear magnetic resonance studies of Cd(II)-substituted blue copper proteins.
abstract: The 113Cd NMR spectra of plastocyanin (Spinacea), stellacyanin (Rhus vernicifera), and two azurins (Pseudomonas aeruginosa and Alcaligenes faecalis) have been measured after introducing Cd(II) into the blue copper-binding sites. Relative to Cd(C1O4)2 the chemical shifts are 432, 380, 372, and 379 ppm, respectively, all of which are found to be reasonable values for binding sites containing a cysteine thiolate ligand. The 113Cd resonances of the cadmium derivatives of stellacyanin and the azurins are so near the same that the proteins must present very similar metal-binding sites. In contrast the plastocyanin derivative resonates about 50 ppm further downfield which may signal a change in coordination number. The spin lattice relaxation times of the 113Cd resonances are of the order of 0.1 s, and a major portion of the relaxation apparently occurs through the chemical shift anisotropy mechanism. At 13 degrees C the 113Cd resonance of Psuedomonas azurin shifts slightly downfield with increasing pH. This is explained by a small change in the environment about cadmium which occurs as a result of the conformational change that attends the titration of His-35.
mesh_terms: D000421:Alcaligenes; D000426:Alcohol Dehydrogenase; D000429:Alcohol Oxidoreductases; D001400:Azurin; D001426:Bacterial Proteins; D002104:Cadmium; D003300:Copper; D009682:Magnetic Resonance Spectroscopy; D010940:Plant Proteins; D010944:Plants; D010947:Plants, Toxic; D010970:Plastocyanin; D011485:Protein Binding; D011550:Pseudomonas aeruginosa; D013045:Species Specificity; D012251:Toxicodendron
chemical_list: D001426:Bacterial Proteins; D010940:Plant Proteins; D002104:Cadmium; D001400:Azurin; D003300:Copper; D010970:Plastocyanin; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase