PDBsum entry 1fqj

Signaling protein

PDB id: 1fqj

Contents

Protein chains

317 a.a. *

133 a.a. *

38 a.a. *

141 a.a. *

Ligands

ALF-GDP ×2

Metals

_MG ×2

Waters ×356

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Structural determinants for regulation of phosphodiesterase by a g protein at 2.0 a.

Authors

K.C.Slep, M.A.Kercher, W.He, C.W.Cowan, T.G.Wensel, P.B.Sigler.

Ref.

Nature, 2001, 409, 1071-1077. [DOI no: 10.1038/35059138]

PubMed id

11234020

Abstract

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.

Figure 3.
Figure 3: PDE bold gamma-/ alpha-[t/i1] interactions. a, A-weighted 2F[o] - F[c] electron density map for [t/i1] GDP AlF^-[4] PDE RGS9 (1.5 ). Anomalous difference Fourier density (15 ) in coral. b, Intermolecular contact (sub 4 Å) matrix for PDE residues (orange) that contact [t/i1] non-switch residues (green) or [t/i1] switch residues (blue). Electrostatic interactions to side chains are shown in red, to main chain in green. van der Waals contacts to side chains, to main chain or to both are shown in black, grey and lavender, respectively. Water-mediated interactions are indicated by blue circles. The root-mean-square deviation (rmsd) for [t/i1] contact residues (C atoms are in black, overall side-chain deviation in grey) is shown for [t/i1] RGS9 versus [t] GTP S (left)6 and [t] GDP AlF^-[4] (right)8. Results of PDE alanine scanning mutagenesis on GTPase stimulation (light-green bars) and K[A] (dark-blue bars; ref. 13) are shown above. c, C trace of PDE [50 -87]. C atoms of residues contacting [t/i1] switch II, the 3/ 3 - 5 loop region or both are in blue, green and orange, respectively. d, CPK representation of PDE W70 in the switch II/ 3 groove with residues that contact W70 in orange. e, Diagram of PDE /switch II/RGS9 interactions coloured as in a. f, CPK representation of the heterotrimeric complex with the five C-terminal amino acids of PDE in red.

Figure 5.
Figure 5: Interaction modes of the G alpha-switch II region with G alpha-effector molecules and the G beta-bold gamma-subunit. a, Interaction of PDE with [t/i1] GDP AlF^-[4]. The colouring scheme is the same as in Fig. 1. b, Interaction of adenylyl cyclase constructs VC[1] (red) and IIC[2] (yellow) with [s] GTP S19. The [s] colouring scheme is homologous to that used for [t/i1] in a. c, Interaction of [259]beta [t] (grey-green) with [260]alpha [t/i1] [261][glyph.gif] GDP (coloured as in a)23.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2001, 409, 1071-1077) copyright 2001.