The rates of exchange of the C-2 protons of histidine residues in copper-zinc superoxide dismutase are substantially decreased by metal ion binding. This observation was used to distinguish between ligand and non ligand histidine residues in bovine and yeast copper-zinc superoxide dismutases; the effect was shown to depend only on metal ion co-ordination and not as a consequence of concomitant changes in protein structure. Selective deuteration of the zinc-only proteins at pH (uncorrected pH-meter reading) 8.2 and 50 degrees C resulted in the distinction between copper and zinc ligand resonances in the 1H n.m.r. spectrum of the enzymes. This method is proposed as a generally applicable technique for identifying histidine residues as ligands in metalloproteins.
The exchange of histidine C-2 protons in superoxide dismutases. A novel method for assigning histidine-metal ligands in proteins
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A E G Cass, H A O Hill, J V Bannister, W H Bannister, V Hasemann, J T Johansen; The exchange of histidine C-2 protons in superoxide dismutases. A novel method for assigning histidine-metal ligands in proteins. Biochem J 1 October 1979; 183 (1): 127–132. doi: https://doi.org/10.1042/bj1830127
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