Tyrosine modification enhances metal-ion binding
- Author(s)
- Baldwin, GS; Bailey, MF; Shehan, BP; Sims, L; Norton, RS;
- Journal Title
- BIOCHEMICAL JOURNAL
- Publication Type
- Journal Article
- 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 CCK8 (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 Fe3+ binding indicated that tyrosine sulfation or phosphorylation increased the stoichiometry from 1 to 2, without greatly affecting the affinity (0.6-2.8 mu M at pH 6.5). Measurement of Ca2+ binding with a Ca2+-selective electrode revealed that phosphorylated CCK8 bound two Ca2+ ions. CCK8 and sulfated CCK8 each bound only one Ca2+ ion with lower affinity. Binding of Ca2+, Zn2+ or Bi3+ to phosphorylated CCK8 did not cause any change in absorbance, but substantially increased the change in absorbance on subsequent addition of Fe3+. 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.
- Publisher
- PORTLAND PRESS LTD
- Keywords
- FERRIC IONS; AGONIST CHOLECYSTOKININ; BIOLOGICAL-ACTIVITY; RECEPTOR; IRON(III); SULFATION; SITE; FLUORESCENCE; SPECTROSCOPY; HYDROLYSIS
- Publisher's Version
- https://doi.org/10.1042/BJ20081059
- Terms of Use/Rights Notice
- Refer to copyright notice on published article.
Creation Date: 2008-11-15 12:00:00