Europium-labeled GTP as a general nonradioactive substitute for [(35)S]GTPgammaS in high-throughput G protein studies

Anal Biochem. 2010 Feb 15;397(2):202-7. doi: 10.1016/j.ab.2009.10.028. Epub 2009 Oct 20.


[(35)S]GTPgammaS, the nonhydrolyzable radioactive GTP analog, has been a powerful tool in G protein studies and has set the standards in this field of research. However, its radioactive nature imposes clear limitations to its use in regular laboratory practice and in high-throughput experimentation. The europium-labeled GTP analog (Eu-GTP) has been used as an alternative in the analysis of G protein activation by G protein-coupled receptors in cellular membrane preparations. Here we expand the usage of Eu-GTP and show that it can be applied in other types of assays where [(35)S]GTPgammaS has been previously utilized. We demonstrate the applicability of the modified Eu-GTP binding technology to analysis of heterotrimeric and monomeric G proteins of natural and recombinant sources, from different organisms, in assays with soluble proteins and membrane-containing assays of a high-throughput format. The deci-nanomolar K(D) of Eu-GTP for the tested G proteins is similar to that of other fluorescent-modified GTP analogs, while the sensitivity achieved in time-resolved fluorescence analysis of Eu-GTP exceeds that of the radioactive measurements. Overall, the results of our modified Eu-GTP binding assay present Eu-GTP as a general nonradioactive alternative for G protein studies, especially attractive in high-throughput experiments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Europium / metabolism*
  • GTP-Binding Proteins / metabolism*
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Guanosine Triphosphate / analogs & derivatives*
  • Guanosine Triphosphate / metabolism
  • Heterotrimeric GTP-Binding Proteins / metabolism
  • Kinetics
  • Organometallic Compounds / metabolism*
  • Receptors, G-Protein-Coupled / metabolism
  • Swine


  • Organometallic Compounds
  • Receptors, G-Protein-Coupled
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Europium
  • Guanosine Triphosphate
  • GTP-Binding Proteins
  • Heterotrimeric GTP-Binding Proteins