 |
PDBsum entry 3c7k
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Signaling protein
|
PDB id
|
|
|
|
3c7k
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
305 a.a.
|
|
|
|
|
|
|
|
|
|
|
119 a.a.
|
|
|
|
|
|
|
|
|
|
|
113 a.a.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Molecular architecture of galphao and the structural basis for rgs16-Mediated deactivation.
|
|
|
Authors
|
|
K.C.Slep,
M.A.Kercher,
T.Wieland,
C.K.Chen,
M.I.Simon,
P.B.Sigler.
|
|
|
Ref.
|
|
Proc Natl Acad Sci U S A, 2008,
105,
6243-6248.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
|
|
