1sbj
From Proteopedia
(New page: 200px<br /><applet load="1sbj" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sbj" /> '''NMR Structure of the Mg2+-loaded C Terminal ...) |
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| - | [[Image:1sbj.jpg|left|200px]]<br /><applet load="1sbj" size=" | + | [[Image:1sbj.jpg|left|200px]]<br /><applet load="1sbj" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1sbj" /> | caption="1sbj" /> | ||
'''NMR Structure of the Mg2+-loaded C Terminal Domain of Cardiac Troponin C Bound to the N Terminal Domain of Cardiac Troponin I'''<br /> | '''NMR Structure of the Mg2+-loaded C Terminal Domain of Cardiac Troponin C Bound to the N Terminal Domain of Cardiac Troponin I'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Cardiac troponin C (cTnC) is the Ca(2+)-binding component of the troponin | + | Cardiac troponin C (cTnC) is the Ca(2+)-binding component of the troponin complex and, as such, is the Ca(2+)-dependent switch in muscle contraction. This protein consists of two globular lobes, each containing a pair of EF-hand metal-binding sites, connected by a linker. In the N lobe, Ca(2+)-binding site I is inactive and Ca(2+)-binding site II is primarily responsible for initiation of muscle contraction. The C lobe contains Ca(2+)/Mg(2+)-binding sites III and IV, which bind Mg(2+) with lower affinity and play a structural as well as a secondary role in modulating the Ca(2+) signal. To understand the structural consequences of Ca(2+)/Mg(2+) exchange in the C lobe, we have determined the NMR solution structure of the Mg(2+)-loaded C lobe, cTnC(81-161), in a complex with the N domain of cardiac troponin I, cTnI(33-80), and compared it with a refined Ca(2+)-loaded structure. The overall tertiary structure of the Mg(2+)-loaded C lobe is very similar to that of the refined Ca(2+)-loaded structure as evidenced by the root-mean-square deviation of 0.94 A for all backbone atoms. While metal-dependent conformational changes are minimal, substitution of Mg(2+) for Ca(2+) is characterized by condensation of the C-terminal portion of the metal-binding loops with monodentate Mg(2+) ligation by the conserved Glu at position 12 and partial closure of the cTnI hydrophobic binding cleft around site IV. Thus, conformational plasticity in the Ca(2+)/Mg(2+)-dependent binding loops may represent a mechanism to modulate C-lobe cTnC interactions with the N domain of cTnI. |
==About this Structure== | ==About this Structure== | ||
| - | 1SBJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with MG as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 1SBJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with <scene name='pdbligand=MG:'>MG</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SBJ OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Gallus gallus]] | [[Category: Gallus gallus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Finley, N | + | [[Category: Finley, N L.]] |
| - | [[Category: Howarth, J | + | [[Category: Howarth, J W.]] |
| - | [[Category: Rosevear, P | + | [[Category: Rosevear, P R.]] |
[[Category: MG]] | [[Category: MG]] | ||
[[Category: 2 magnesium binding protein]] | [[Category: 2 magnesium binding protein]] | ||
| Line 22: | Line 22: | ||
[[Category: troponin c-troponin i interaction]] | [[Category: troponin c-troponin i interaction]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:59:51 2008'' |
Revision as of 12:59, 21 February 2008
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NMR Structure of the Mg2+-loaded C Terminal Domain of Cardiac Troponin C Bound to the N Terminal Domain of Cardiac Troponin I
Overview
Cardiac troponin C (cTnC) is the Ca(2+)-binding component of the troponin complex and, as such, is the Ca(2+)-dependent switch in muscle contraction. This protein consists of two globular lobes, each containing a pair of EF-hand metal-binding sites, connected by a linker. In the N lobe, Ca(2+)-binding site I is inactive and Ca(2+)-binding site II is primarily responsible for initiation of muscle contraction. The C lobe contains Ca(2+)/Mg(2+)-binding sites III and IV, which bind Mg(2+) with lower affinity and play a structural as well as a secondary role in modulating the Ca(2+) signal. To understand the structural consequences of Ca(2+)/Mg(2+) exchange in the C lobe, we have determined the NMR solution structure of the Mg(2+)-loaded C lobe, cTnC(81-161), in a complex with the N domain of cardiac troponin I, cTnI(33-80), and compared it with a refined Ca(2+)-loaded structure. The overall tertiary structure of the Mg(2+)-loaded C lobe is very similar to that of the refined Ca(2+)-loaded structure as evidenced by the root-mean-square deviation of 0.94 A for all backbone atoms. While metal-dependent conformational changes are minimal, substitution of Mg(2+) for Ca(2+) is characterized by condensation of the C-terminal portion of the metal-binding loops with monodentate Mg(2+) ligation by the conserved Glu at position 12 and partial closure of the cTnI hydrophobic binding cleft around site IV. Thus, conformational plasticity in the Ca(2+)/Mg(2+)-dependent binding loops may represent a mechanism to modulate C-lobe cTnC interactions with the N domain of cTnI.
About this Structure
1SBJ is a Single protein structure of sequence from Gallus gallus with as ligand. Full crystallographic information is available from OCA.
Reference
Structure of the Mg2+-loaded C-lobe of cardiac troponin C bound to the N-domain of cardiac troponin I: comparison with the Ca2+-loaded structure., Finley NL, Howarth JW, Rosevear PR, Biochemistry. 2004 Sep 14;43(36):11371-9. PMID:15350124
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