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Title: Structural Basis for Inhibition of Mammalian Adenylyl Cyclase by Calcium

Abstract

Type V and VI mammalian adenylyl cyclases (AC5, AC6) are inhibited by Ca{sup 2+} at both sub- and supramicromolar concentration. This inhibition may provide feedback in situations where cAMP promotes opening of Ca{sup 2+} channels, allowing fine control of cardiac contraction and rhythmicity in cardiac tissue where AC5 and AC6 predominate. Ca{sup 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{sub i} = {approx}0.4 {mu}M) and 'low-affinity' (K{sub i} = {approx}100 {mu}M) modes of inhibition. At micromolar concentration, Ca{sup 2+} inhibition is nonexclusive with respect to pyrophosphate (PP{sub i}), a noncompetitive inhibitor with respect to ATP, but at >100 {mu}M Ca{sup 2+}, inhibition appears to be exclusive with respect to PP{sub i}. The 3.0 {angstrom} resolution structure of G{alpha}s{center_dot}GTP{gamma}S/forskolin-activated VC1:IIC2 crystals soaked in the presence of ATP{alpha}S and 8 {mu}M free Ca{sup 2+} contains a single, loosely coordinated metal ion. ATP soaked into VC1:IIC2 crystals in the presence of 1.5 mM Ca{sup 2+} is not cyclized, and two calcium ions are observed in the 2.9 {angstrom} resolution structure of the complex. In both of the latter complexes VC1:IIC2more » 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{sup 2+} or Mn{sup 2+}. Structures of the pyrophosphate (PP{sub i}) complex with 10 mM Mg{sup 2+} (2.8 {angstrom}) or 2 mM Ca{sup 2+} (2.7 {angstrom}) also adopt the open conformation, indicating that the closed to open transition occurs after cAMP release. In the latter complexes, Ca{sup 2+} and Mg{sup 2+} bind only to the high-affinity 'B' metal site associated with substrate/product stabilization. Ca{sup 2+} thus stabilizes the inactive conformation in both ATP- and PP{sub i}-bound states.« less

Authors:
; ; ; ;  [1];  [1]
  1. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1005686
Resource Type:
Journal Article
Journal Name:
Biochemistry-US
Additional Journal Information:
Journal Volume: 48; Journal Issue: (15) ; 02, 2009; Journal ID: ISSN 0006-2960
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 74 ATOMIC AND MOLECULAR PHYSICS; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; AMP; ATP; CALCIUM; CALCIUM IONS; COMPLEXES; CONTRACTION; CONTROL; CRYSTALS; CYCLASES; FEEDBACK; INHIBITION; METALS; PYROPHOSPHATES; RESOLUTION; RHYTHMICITY; STABILIZATION

Citation Formats

Mou, Tung-Chung, Masada, Nanako, Cooper, Dermot M.F., Sprang, Stephen R., Cambridge), and Montana). Structural Basis for Inhibition of Mammalian Adenylyl Cyclase by Calcium. United States: N. p., 2009. Web. doi:10.1021/bi802122k.
Mou, Tung-Chung, Masada, Nanako, Cooper, Dermot M.F., Sprang, Stephen R., Cambridge), & Montana). Structural Basis for Inhibition of Mammalian Adenylyl Cyclase by Calcium. United States. doi:10.1021/bi802122k.
Mou, Tung-Chung, Masada, Nanako, Cooper, Dermot M.F., Sprang, Stephen R., Cambridge), and Montana). Fri . "Structural Basis for Inhibition of Mammalian Adenylyl Cyclase by Calcium". United States. doi:10.1021/bi802122k.
@article{osti_1005686,
title = {Structural Basis for Inhibition of Mammalian Adenylyl Cyclase by Calcium},
author = {Mou, Tung-Chung and Masada, Nanako and Cooper, Dermot M.F. and Sprang, Stephen R. and Cambridge) and Montana)},
abstractNote = {Type V and VI mammalian adenylyl cyclases (AC5, AC6) are inhibited by Ca{sup 2+} at both sub- and supramicromolar concentration. This inhibition may provide feedback in situations where cAMP promotes opening of Ca{sup 2+} channels, allowing fine control of cardiac contraction and rhythmicity in cardiac tissue where AC5 and AC6 predominate. Ca{sup 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{sub i} = {approx}0.4 {mu}M) and 'low-affinity' (K{sub i} = {approx}100 {mu}M) modes of inhibition. At micromolar concentration, Ca{sup 2+} inhibition is nonexclusive with respect to pyrophosphate (PP{sub i}), a noncompetitive inhibitor with respect to ATP, but at >100 {mu}M Ca{sup 2+}, inhibition appears to be exclusive with respect to PP{sub i}. The 3.0 {angstrom} resolution structure of G{alpha}s{center_dot}GTP{gamma}S/forskolin-activated VC1:IIC2 crystals soaked in the presence of ATP{alpha}S and 8 {mu}M free Ca{sup 2+} contains a single, loosely coordinated metal ion. ATP soaked into VC1:IIC2 crystals in the presence of 1.5 mM Ca{sup 2+} is not cyclized, and two calcium ions are observed in the 2.9 {angstrom} 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{sup 2+} or Mn{sup 2+}. Structures of the pyrophosphate (PP{sub i}) complex with 10 mM Mg{sup 2+} (2.8 {angstrom}) or 2 mM Ca{sup 2+} (2.7 {angstrom}) also adopt the open conformation, indicating that the closed to open transition occurs after cAMP release. In the latter complexes, Ca{sup 2+} and Mg{sup 2+} bind only to the high-affinity 'B' metal site associated with substrate/product stabilization. Ca{sup 2+} thus stabilizes the inactive conformation in both ATP- and PP{sub i}-bound states.},
doi = {10.1021/bi802122k},
journal = {Biochemistry-US},
issn = {0006-2960},
number = (15) ; 02, 2009,
volume = 48,
place = {United States},
year = {2009},
month = {9}
}