The Mechanistic Role of Metal Ions, Ca2+ and Mg2+, in RGS: G‐Protein Interactions

Abstract

Regulator of G protein signaling (RGS) proteins are negative regulators of G protein‐coupled receptor (GPCR) signaling through their ability to act as GTPase activating proteins (GAPs) for activated Gα subunits. The RZ subfamily, of which RGS17 is a member, binds to activated Gαo, Gαz, and Gαi1–3 proteins to modulate downstream pathways, including those involved in formation of cyclic AMP and Ca2+‐dependent signaling. In contrast to other RGS proteins, less is known about the regulation of RZ family members. Both crystallization and 1H‐15N 2D HSQC NMR experiments revealed a putative interaction of the metal ion Ca2+ with RGS17 at a defined binding site. Subsequent protein‐protein interaction experiments, using AlphaScreen were used to assess the impact on the ions Ca2+ and Mg2+ on the RGS17 interaction with activated Gαo. The results indicate that both calcium and magnesium have an effect of promoting the RGS17 ‐ Gαo interaction. These studies will extend to examining the selectivity and affinity of RGS17 for other physiologically relevant divalent metal cations, such as Zn2+, Cu2+, and Mn2+. In addition, the residues of RGS17 that bind Ca2+ are conserved in multiple RGS proteins. The functional impact of metal ion binding is likely not limited to RGS17 and a more in‐depth evaluation of these proteins for metal binding deserves further attention.Support or Funding InformationThis work was supported by The University of Iowa Center for Biocatalysis and Bioprocessing and the NIH‐sponsored Predoctoral Training Program in Biotechnology (2 T32 GM008365).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.