Specific binding of RGS9-Gbeta 5L to protein anchor in photoreceptor membranes greatly enhances its catalytic activity

J Biol Chem. 2002 Jul 5;277(27):24376-81. doi: 10.1074/jbc.M203237200. Epub 2002 May 2.


The complex between the short splice variant of the ninth member of the RGS protein family and the long splice variant of type 5 G protein beta subunit (RGS9-Gbeta5L) plays a critical role in regulating the duration of the light response in vertebrate photoreceptors by activating the GTPase activity of the photoreceptor-specific G protein, transducin. RGS9-Gbeta5L is tightly associated with the membranes of photoreceptor outer segments; however, the nature of this association remains unknown. Here we demonstrate that rod outer segment membranes contain a limited number of sites for high affinity RGS9-Gbeta5L binding, which are highly sensitive to proteolysis. In membranes isolated from bovine rod outer segments, all of these sites are occupied by the endogenous RGS9-Gbeta5L, which prevents the binding of exogenous recombinant RGS9-Gbeta5L to these sites. However, treating membranes with urea or high pH buffers causes either removal or denaturation of the endogenous RGS9-Gbeta5L, allowing for high affinity binding of recombinant RGS9-Gbeta5L to these sites. This binding results in a striking approximately 70-fold increase in the RGS9-Gbeta5L ability to activate transducin GTPase. The DEP (disheveled/EGL-10/pleckstrin) domain of RGS9 plays a crucial role in the RGS9-Gbeta5L membrane attachment, as evident from the analysis of membrane-binding properties of deletion mutants lacking either N- or C-terminal parts of the RGS9 molecule. Our data indicate that specific association of RGS9-Gbeta5L with photoreceptor disc membranes serves not only as a means of targeting it to an appropriate subcellular compartment but also serves as an important determinant of its catalytic activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Binding Sites
  • Catalysis
  • Cattle
  • Cell Membrane / metabolism
  • Kinetics
  • Mutagenesis, Site-Directed
  • Photoreceptor Cells, Vertebrate / metabolism*
  • RGS Proteins / chemistry
  • RGS Proteins / genetics
  • RGS Proteins / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Retina / metabolism*
  • Rod Cell Outer Segment / metabolism*


  • RGS Proteins
  • Recombinant Proteins
  • regulator of g-protein signaling 9