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.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511, USA. kcs@mail.csb.yale.edu
K C
KC
Slep
M A
MA
Kercher
W
W
He
C W
CW
Cowan
T G
TG
Wensel
P B
PB
Sigler
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