3C14: Complex Of Gs-Alpha With The Catalytic Domains Of Mammalian Adenylyl Cyclase: Complex With Pyrophosphate And Ca

Citation:
Abstract
Type V and VI mammalian adenylyl cyclases (AC5, AC6) are inhibited by Ca(2+) at both sub- and supramicromolar concentration. This inhibition may provide feedback in situations where cAMP promotes opening of Ca(2+) channels, allowing fine control of cardiac contraction and rhythmicity in cardiac tissue where AC5 and AC6 predominate. Ca(2+) inhibits the soluble AC core composed of the C1 domain of AC5 (VC1) and the C2 domain of AC2 (IIC2). As observed for holo-AC5, inhibition is biphasic, showing "high-affinity" (K(i) = approximately 0.4 microM) and "low-affinity" (K(i) = approximately 100 microM) modes of inhibition. At micromolar concentration, Ca(2+) inhibition is nonexclusive with respect to pyrophosphate (PP(i)), a noncompetitive inhibitor with respect to ATP, but at >100 microM Ca(2+), inhibition appears to be exclusive with respect to PP(i). The 3.0 A resolution structure of Galphas.GTPgammaS/forskolin-activated VC1:IIC2 crystals soaked in the presence of ATPalphaS and 8 microM free Ca(2+) contains a single, loosely coordinated metal ion. ATP soaked into VC1:IIC2 crystals in the presence of 1.5 mM Ca(2+) is not cyclized, and two calcium ions are observed in the 2.9 A resolution structure of the complex. In both of the latter complexes VC1:IIC2 adopts the "open", catalytically inactive conformation characteristic of the apoenzyme, in contrast to the "closed", active conformation seen in the presence of ATP analogues and Mg(2+) or Mn(2+). Structures of the pyrophosphate (PP(i)) complex with 10 mM Mg(2+) (2.8 A) or 2 mM Ca(2+) (2.7 A) also adopt the open conformation, indicating that the closed to open transition occurs after cAMP release. In the latter complexes, Ca(2+) and Mg(2+) bind only to the high-affinity "B" metal site associated with substrate/product stabilization. Ca(2+) thus stabilizes the inactive conformation in both ATP- and PP(i)-bound states.
PDB ID: 3C14Download
MMDB ID: 69398
PDB Deposition Date: 2008/1/22
Updated in MMDB: 2011/08
Experimental Method:
x-ray diffraction
Resolution: 2.68  Å
Source Organism:
Rattus norvegicus
Similar Structures:
Biological Unit for 3C14: trimeric; determined by author and by software (PISA)
Molecular Components in 3C14
Label Count Molecule
Proteins (3 molecules)
1
Adenylate Cyclase Type 5(Gene symbol: ADCY5)
Molecule annotation
1
Adenylate Cyclase Type 2(Gene symbol: Adcy2)
Molecule annotation
1
Guanine Nucleotide-binding Protein G(s) Subunit Alpha Isoforms Short(Gene symbol: GNAS)
Molecule annotation
Chemicals (6 molecules)
1
1
2
1
3
1
4
1
5
1
6
1
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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