Structural determinants for regulation of phosphodiesterase by a G protein at 2.0 A.
A multitude of heptahelical receptors use heterotrimeric G proteins to transduce signals to specific effector target molecules. The G protein transducin, Gt, couples photon-activated rhodopsin with the effector cyclic GMP phosophodiesterase (PDE) in the vertebrate phototransduction cascade. The interactions of the Gt alpha-subunit (alpha(t)) with the inhibitory PDE gamma-subunit (PDEgamma) are central to effector activation, and also enhance visual recovery in cooperation with the GTPase-activating protein regulator of G-protein signalling (RGS)-9 (refs 1-3). Here we describe the crystal structure at 2.0 A of rod transducin alpha x GDP x AlF4- in complex with the effector molecule PDEgamma and the GTPase-activating protein RGS9. In addition, we present the independently solved crystal structures of the RGS9 RGS domain both alone and in complex with alpha(t/i1) x GDP x AlF4-. These structures reveal insights into effector activation, synergistic GTPase acceleration, RGS9 specificity and RGS activity. Effector binding to a nucleotide-dependent site on alpha(t) sequesters PDEgamma residues implicated in PDE inhibition, and potentiates recruitment of RGS9 for hydrolytic transition state stabilization and concomitant signal termination.
Slep
K C
KC
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA. kcs@mail.csb.yale.edu
Kercher
M A
MA
He
W
W
Cowan
C W
CW
Wensel
T G
TG
Sigler
P B
PB
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D020710:RGS Proteins / Q000737:chemistry / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000737:chemistry / Q000201:enzymology; D016415:Sequence Alignment; D015293:Transducin / Q000737:chemistry / Q000378:metabolism
D020710:RGS Proteins; C116925:regulator of g-protein signaling 9; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D019204:GTP-Binding Proteins; D015293:Transducin