1scv: Difference between revisions
New page: left|200px<br /><applet load="1scv" size="450" color="white" frame="true" align="right" spinBox="true" caption="1scv" /> '''NMR STRUCTURE OF THE C TERMINAL DOMAIN OF CA... |
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'''NMR STRUCTURE OF THE C TERMINAL DOMAIN OF CARDIAC TROPONIN C BOUND TO THE N TERMINAL DOMAIN OF CARDIAC TROPONIN I'''<br /> | '''NMR STRUCTURE OF THE 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== | ||
1SCV 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 CA as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | 1SCV 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=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SCV 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: CA]] | [[Category: CA]] | ||
[[Category: calcium binding protein]] | [[Category: calcium binding protein]] | ||
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[[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 15:00:14 2008'' | ||
Revision as of 16:00, 21 February 2008
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NMR STRUCTURE OF THE C TERMINAL DOMAIN OF CARDIAC TROPONIN C BOUND TO THE N TERMINAL DOMAIN OF CARDIAC TROPONIN I
OverviewOverview
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 StructureAbout this Structure
1SCV is a Single protein structure of sequence from Gallus gallus with as ligand. Full crystallographic information is available from OCA.
ReferenceReference
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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