• DOI:10.1021/BI00007A002
• Corpus ID: 21803520

A divalent metal ion binding site in the kinase insert domain of the alpha-platelet-derived growth factor receptor regulates its association with SH2 domains.

@article{Mahadevan1995ADM,
  title={A divalent metal ion binding site in the kinase insert domain of the alpha-platelet-derived growth factor receptor regulates its association with SH2 domains.},
  author={Daruka Mahadevan and Narmada Thanki and Pilar Aroca and Peter McPhie and J. C. Yu and John F. Beeler and Eugenio Santos and Alexander Wlodawer and Mohammad A. Heidaran},
  journal={Biochemistry},
  year={1995},
  volume={34 7},
  pages={
          2095-106
        }
}

• D. Mahadevan, N. Thanki, +6 authors M. Heidaran
• Published 21 February 1995
• Biology
• Biochemistry

To investigate the effects of metal ion binding to the alpha-PDGFR kinase insert domain, a PCR product representing amino acid residues 691-795 (104 amino acids) was bacterially expressed and purified. Secondary structure prediction and circular dichroism spectroscopy indicated this domain to be a mixed alpha + beta protein with a large coil/turn contribution. This 16 kDa, soluble, nonphosphorylated domain bound to 45Ca2+ and 65Zn2+ through a common shared site. Of the unlabeled divalent and trivalent metal ions tested, Ho3+ = Zn2+ > Ni2+ > Ca2+ = Mn2+ > Mg2+, Ba2+ in competing for 45Ca2+ binding to this domain. In the presence of Ca2+ ions, the conformation of the KI domain changed significantly, and this changed conformation was resistant to subtilisin proteolysis. However, in the presence of Zn2+ ions, the conformation of the KI domain changed only slightly. Nevertheless, Zn2+ ions were more effective in rendering the KI domain resistant to proteolysis as compared to that shown by Ca2+ ions. In vitro binding studies using purified baculovirus-expressed alpha-PDGFR showed a marked increase in binding the p85 N-SH2 domain in the presence of Ca2+ or Zn2+ ions (KD = 0.5 microM), suggesting that metal ion binding enhances association of the p85 N-SH2 domain with the receptor. To confirm this, association of the alpha-PDGFR with the p85 N-SH2 domain was tested in the presence of the KI domain. The nonphosphorylated KI domain was effective in competing with the alpha-PDGFR for the binding of the p85 N-SH2 domain. This effect was more pronounced in the presence of Ca2+ ions. Microinjection of this domain into Xenopus oocytes delayed maturation in the presence of insulin but not progesterone. This suggests that the KI domain has a correctly folded three-dimensional structure compatible with biological activity. Together these findings indicate that the recombinant alpha-PDGFR KI domain binds the p85 N-SH2 domain and this binding is modulated by the presence of a novel divalent metal ion binding site within its structure.