PDBsum entry 2bcj

Transferase/hydrolase

PDB id: 2bcj

Contents

Protein chains

624 a.a.

340 a.a.

64 a.a.

317 a.a.

Ligands

ALF-GDP

Metals

_MG

Waters ×5

References listed in PDB file

Key reference

Title

Snapshot of activated g proteins at the membrane: the galphaq-Grk2-Gbetagamma complex.

Authors

V.M.Tesmer, T.Kawano, A.Shankaranarayanan, T.Kozasa, J.J.Tesmer.

Ref.

Science, 2005, 310, 1686-1690. [DOI no: 10.1126/science.1118890]

PubMed id

16339447

Abstract

G protein-coupled receptor kinase 2 (GRK2) plays a key role in the desensitization of G protein-coupled receptor signaling by phosphorylating activated heptahelical receptors and by sequestering heterotrimeric G proteins. We report the atomic structure of GRK2 in complex with Galphaq and Gbetagamma, in which the activated Galpha subunit of Gq is fully dissociated from Gbetagamma and dramatically reoriented from its position in the inactive Galphabetagamma heterotrimer. Galphaq forms an effector-like interaction with the GRK2 regulator of G protein signaling (RGS) homology domain that is distinct from and does not overlap with that used to bind RGS proteins such as RGS4.

Figure 1.
Fig. 1. Comparison of the inactive G ß heterotrimer and the G [i/q]-GRK2-Gß complex. (A) Side view of G [q]ß . G [q]ß was homology modeled by using the structure of G [i]ß[1] [2] (5). The expected membrane surface is modeled as a gray rectangle that extends out from the plane of the figure (31), and the heterotrimer is oriented as proposed in (6). G [q] is cyan with orange ß-strands, Gß is blue, and G is green. The three switch regions (labeled I, II, and III) and the N-terminal helix of G [q] are red and yellow, respectively. GDP and G [q]-Cys9 and Cys10, which can be palmitoylated, are shown as ball-and-stick models. (B) Top view of G [q]ß from the perspective of the modeled membrane surface. (C) Side view of the G [i/q]-GRK2-Gß complex. For purposes of comparison, GRK2-bound Gß was centered in the same position as Gß in panel (A). The chimeric N-terminal helix of GRK2-bound G [i/q] is disordered in the crystal structure. The kinase domain of GRK2 is yellow with olive ß strands, the RH domain is purple, and the PH domain is tan. Mg2+ (black sphere) and AIF[4]^- (green and magenta) are bound in the active site of G [i/q]. (D) Top view of the G [i/q]-GRK2-Gß complex from the same orientation as (B). Residues 114 to 121 in 5 of GRK2 (shaded pink) alter their conformation upon docking with the effector-binding pocket of G [i/q] (see SOM text).

Figure 3.
Fig. 3. The GRK2-binding surface of G [q]. (A) Stereoview of the interface. The switch II and 3 helices from G [i/q] are shown as C traces; the 5 and 6 helices from GRK2 are shown as cartoon ribbons. Side chains of interfacial residues are shown as ball-and-stick models, with carbon atoms from G [i/q] and GRK2 colored cyan and yellow, respectively. Hydrogen bonds are shown as dashed black lines. Residues targeted by site-directed mutagenesis in this study are underlined. (B) Sequence alignment of the switch regions and the 3/ß5 sequence for representative members of all four G subfamilies. Switch regions (I to III) are outlined in black and are assigned on the basis of comparison of the active and deactivated structures of G [i1]. Secondary structure is represented by cylinders and arrows for helices and ß strands, respectively. G residues that contact effectors are green, those that bind GAPs are red, and those that contact both are purple. Contacting residues that were chimeric (i.e., nonnative) in the crystal structures of the G [t] and G [13] effector complexes are shown in a lighter shade of the appropriate color. Green boxes outline G [i] residues proposed to interact with adenylyl cyclase (50), and asterisks indicate conserved residues that contribute to the hydrophobic effector-binding pocket. The crystal structures used for these assignments are those of G [i/q]-GRK2-Gß (this study), G [i]-RGS4 [Protein Data Bank (PDB) code 1AGR [PDB] ] (12), G [t]-PDE -RGS9 (1FQJ) (8), G [13]-p115RhoGEF (1SHZ) (10), and G [s]-adenylyl cyclase (1AZS) (7). The sequences are those of mouse G [q] (M55412 [GenBank] ), mouse G [11] (NP_034431 [GenBank] ), mouse G [14] (NP_032163 [GenBank] ), human G [16] (M63904 [GenBank] ), rat G [i1] (M17527 [GenBank] ), bovine G [t] (P04695 [GenBank] ), mouse G [13] (NP_034433 [GenBank] ), and bovine G [s] (M13006 [GenBank] ). (C) Mutational analysis of G [q] residues that directly interact with GRK2. Lysates of HEK293 cells expressing G [q] mutants were subjected to limited trypsin digestion in the presence and absence (shown only for wild type) of and immunoblotted with G [q]-specific antibody (upper left) (31).

The above figures are reprinted by permission from the AAAs: Science (2005, 310, 1686-1690) copyright 2005.