PDBsum entry 3c7k

Signaling protein

PDB id: 3c7k

Contents

Protein chains

305 a.a. *

119 a.a. *

113 a.a. *

Ligands

ALF ×2

GDP ×2

Metals

_MG ×2

Waters ×6

* Residue conservation analysis

PDB id:

3c7k

Name:

Signaling protein

Title:

Molecular architecture of galphao and the structural basis for rgs16- mediated deactivation

Structure:

Guanine nucleotide-binding protein g(o) subunit alpha. Chain: a, c. Fragment: residues 22-354. Synonym: guanine nucleotide-binding protein g(o) subunit alpha. Engineered: yes. Regulator of g-protein signaling 16. Chain: b, d. Fragment: residues 53-180. Synonym: rgs16, retinally abundant regulator of g-protein signaling,

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Gene: gnao1, gna0, gnao. Expressed in: escherichia coli bl21. Expression_system_taxid: 511693. Gene: rgs16, rgsr.

Resolution:

2.90Å R-factor: 0.250 R-free: 0.311

Authors:

K.C.Slep,M.A.Kercher,T.Wieland,C.Chen,M.I.Simon,P.B.Sigler

Key ref:

K.C.Slep et al. (2008). Molecular architecture of Galphao and the structural basis for RGS16-mediated deactivation. Proc Natl Acad Sci U S A, 105, 6243-6248. PubMed id: 18434540 DOI: 10.1073/pnas.0801569105

Date:

07-Feb-08 Release date: 06-May-08

Protein chains

P18872  (GNAO_MOUSE) -  Guanine nucleotide-binding protein G(o) subunit alpha from Mus musculus

Seq: 354 a.a.

Struc: 305 a.a.

Protein chain

P97428  (RGS16_MOUSE) -  Regulator of G-protein signaling 16 from Mus musculus

Seq: 201 a.a.

Struc: 119 a.a.

Protein chain

P97428  (RGS16_MOUSE) -  Regulator of G-protein signaling 16 from Mus musculus

Seq: 201 a.a.

Struc: 113 a.a.

DOI no: 10.1073/pnas.0801569105

Proc Natl Acad Sci U S A 105:6243-6248 (2008)

PubMed id: 18434540

Molecular architecture of Galphao and the structural basis for RGS16-mediated deactivation.

K.C.Slep, M.A.Kercher, T.Wieland, C.K.Chen, M.I.Simon, P.B.Sigler.

ABSTRACT

Heterotrimeric G proteins relay extracellular cues from heptahelical transmembrane receptors to downstream effector molecules. Composed of an alpha subunit with intrinsic GTPase activity and a betagamma heterodimer, the trimeric complex dissociates upon receptor-mediated nucleotide exchange on the alpha subunit, enabling each component to engage downstream effector targets for either activation or inhibition as dictated in a particular pathway. To mitigate excessive effector engagement and concomitant signal transmission, the Galpha subunit's intrinsic activation timer (the rate of GTP hydrolysis) is regulated spatially and temporally by a class of GTPase accelerating proteins (GAPs) known as the regulator of G protein signaling (RGS) family. The array of G protein-coupled receptors, Galpha subunits, RGS proteins and downstream effectors in mammalian systems is vast. Understanding the molecular determinants of specificity is critical for a comprehensive mapping of the G protein system. Here, we present the 2.9 A crystal structure of the enigmatic, neuronal G protein Galpha(o) in the GTP hydrolytic transition state, complexed with RGS16. Comparison with the 1.89 A structure of apo-RGS16, also presented here, reveals plasticity upon Galpha(o) binding, the determinants for GAP activity, and the structurally unique features of Galpha(o) that likely distinguish it physiologically from other members of the larger Galpha(i) family, affording insight to receptor, GAP and effector specificity.

Selected figure(s)

Figure 2.
Gα[o]–RGS16 contacts and the RGS domain GAP mechanism. (A) Stick-and-ribbons diagram of the Gα[o] GTP binding pocket occupied by the transition state analog of GTP hydrolysis; GDP·AlF[4] ^− is shown with Mg^2+ and the attacking water. Gα[o] is shown in green and orange (switch regions). RGS16 is shown in purple. RGS16 residues do not contact the GTP or attacking water directly; instead they buttress the endogenous catalytic residues of Gα[o], stabilizing their conformation in the transition state. (B) Comparative <4 Å electrostatic interaction matrix between RGS16 and Gα subunits. Electrostatic interactions between mouse Gα[o] and mouse RGS16 are indicated in green. Electrostatic interactions between human Gα[i1] and human RGS16 are indicated in yellow (PDB ID code 2IK8; see ref. 18). Gα switch residues are boxed in orange; helical domain residues are boxed in purple. Interactions that occur in one or both crystallographic protomers are included for both Gα[o]–RGS16 and Gα[i1]–RGS16.

Figure 3.
Determinants of RGS16 binding and conformational plasticity. Structural alignment of mouse RGS16 in the free (gray) and Gα[o]-bound (slate) states. The Cα trace is presented for both structures, with key residues used in the Gα[o] interaction represented in stick format. The structural alignment was performed with PyMol.

Figures were selected by an automated process.