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|Title:||Tyrosine modification enhances metal-ion binding.|
|Authors:||Baldwin, Graham S;Bailey, Michael F;Shehan, B Philip;Sims, Ioulia;Norton, Raymond S|
The University of Melbourne Department of Surgery, Austin Health, Heidelberg, Victoria 3084, Australia
|Citation:||The Biochemical Journal; 416(1): 77-84|
|Abstract:||Tyrosine sulfation is a common modification of many proteins, and the ability to phosphorylate tyrosine residues is an intrinsic property of many growth-factor receptors. In the present study, we have utilized the peptide hormone CCK(8) (cholecystokinin), which occurs naturally in both sulfated and unsulfated forms, as a model to investigate the effect of tyrosine modification on metal-ion binding. The changes in absorbance and fluorescence emission on Fe(3+) binding indicated that tyrosine sulfation or phosphorylation increased the stoichiometry from 1 to 2, without greatly affecting the affinity (0.6-2.8 microM at pH 6.5). Measurement of Ca(2+) binding with a Ca(2+)-selective electrode revealed that phosphorylated CCK(8) bound two Ca(2+) ions. CCK(8) and sulfated CCK(8) each bound only one Ca(2+) ion with lower affinity. Binding of Ca(2+), Zn(2+) or Bi(3+) to phosphorylated CCK(8) did not cause any change in absorbance, but substantially increased the change in absorbance on subsequent addition of Fe(3+). The results of the present study demonstrate that tyrosine modification may increase the affinity of metal-ion binding to peptides, and imply that metal ions may directly regulate many signalling pathways.|
|Internal ID Number:||18636967|
Tyrosine.analogs & derivatives.chemistry.metabolism
|Appears in Collections:||Journal articles|
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