RGS12 and RGS14 GoLoco motifs are G alpha(i) interaction sites with guanine nucleotide dissociation inhibitor Activity.
The regulators of G-protein signaling (RGS) proteins accelerate the intrinsic guanosine triphosphatase activity of heterotrimeric G-protein alpha subunits and are thus recognized as key modulators of G-protein-coupled receptor signaling. RGS12 and RGS14 contain not only the hallmark RGS box responsible for GTPase-accelerating activity but also a single G alpha(i/o)-Loco (GoLoco) ... motif predicted to represent a second G alpha interaction site. Here, we describe functional characterization of the GoLoco motif regions of RGS12 and RGS14. Both regions interact exclusively with G alpha(i1), G alpha(i2), and G alpha(i3) in their GDP-bound forms. In GTP gamma S binding assays, both regions exhibit guanine nucleotide dissociation inhibitor (GDI) activity, inhibiting the rate of exchange of GDP for GTP by G alpha(i1). Both regions also stabilize G alpha(i1) in its GDP-bound form, inhibiting the increase in intrinsic tryptophan fluorescence stimulated by AlF(4)(-). Our results indicate that both RGS12 and RGS14 harbor two distinctly different G alpha interaction sites: a previously recognized N-terminal RGS box possessing G alpha(i/o) GAP activity and a C-terminal GoLoco region exhibiting G alpha(i) GDI activity. The presence of two, independent G alpha interaction sites suggests that RGS12 and RGS14 participate in a complex coordination of G-protein signaling beyond simple G alpha GAP activity.
Mesh Terms:
Aluminum Compounds, Amino Acid Sequence, Amino Acid Substitution, Animals, Binding Sites, Biosensing Techniques, Cloning, Molecular, Escherichia coli, Fluorides, Guanosine 5'-O-(3-Thiotriphosphate), Guanosine Diphosphate, Heterotrimeric GTP-Binding Proteins, Kinetics, Models, Biological, Molecular Sequence Data, Mutagenesis, Site-Directed, Oligopeptides, Open Reading Frames, RGS Proteins, Rats, Recombinant Proteins, Signal Transduction, Surface Plasmon Resonance
Aluminum Compounds, Amino Acid Sequence, Amino Acid Substitution, Animals, Binding Sites, Biosensing Techniques, Cloning, Molecular, Escherichia coli, Fluorides, Guanosine 5'-O-(3-Thiotriphosphate), Guanosine Diphosphate, Heterotrimeric GTP-Binding Proteins, Kinetics, Models, Biological, Molecular Sequence Data, Mutagenesis, Site-Directed, Oligopeptides, Open Reading Frames, RGS Proteins, Rats, Recombinant Proteins, Signal Transduction, Surface Plasmon Resonance
J. Biol. Chem.
Date: Aug. 03, 2001
PubMed ID: 11387333
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