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==NMR structure of the N-domain of troponin C bound to switch region of troponin I and 3-methyldiphenylamine (solvent exposed mode)==
<StructureSection load='5wcl' size='340' side='right'caption='[[5wcl]]' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5wcl]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5WCL OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5WCL FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=9XG:3-methyl-N-phenylaniline'>9XG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5wcl FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5wcl OCA], [https://pdbe.org/5wcl PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5wcl RCSB], [https://www.ebi.ac.uk/pdbsum/5wcl PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5wcl ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/TNNC1_HUMAN TNNC1_HUMAN] Defects in TNNC1 are the cause of cardiomyopathy dilated type 1Z (CMD1Z) [MIM:[https://omim.org/entry/611879 611879]. Dilated cardiomyopathy is a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death.<ref>PMID:15542288</ref>   Defects in TNNC1 are the cause of familial hypertrophic cardiomyopathy type 13 (CMH13) [MIM:[https://omim.org/entry/613243 613243]. A hereditary heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death.<ref>PMID:11385718</ref> <ref>PMID:16302972</ref> <ref>PMID:18572189</ref> <ref>PMID:19439414</ref> [https://www.uniprot.org/uniprot/TNNI3_HUMAN TNNI3_HUMAN] Defects in TNNI3 are the cause of familial hypertrophic cardiomyopathy type 7 (CMH7) [MIM:[https://omim.org/entry/613690 613690]. Familial hypertrophic cardiomyopathy is a hereditary heart disorder characterized by ventricular hypertrophy, which is usually asymmetric and often involves the interventricular septum. The symptoms include dyspnea, syncope, collapse, palpitations, and chest pain. They can be readily provoked by exercise. The disorder has inter- and intrafamilial variability ranging from benign to malignant forms with high risk of cardiac failure and sudden cardiac death.<ref>PMID:9241277</ref> <ref>PMID:11815426</ref> <ref>PMID:12707239</ref> <ref>PMID:12974739</ref> <ref>PMID:16199542</ref>   Defects in TNNI3 are the cause of familial restrictive cardiomyopathy type 1 (RCM1) [MIM:[https://omim.org/entry/115210 115210]. RCM1 is a heart muscle disorder characterized by impaired filling of the ventricles with reduced diastolic volume, in the presence of normal or near normal wall thickness and systolic function.<ref>PMID:12531876</ref>   Defects in TNNI3 are the cause of cardiomyopathy dilated type 2A (CMD2A) [MIM:[https://omim.org/entry/611880 611880]. Dilated cardiomyopathy is a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death.<ref>PMID:15070570</ref>   Defects in TNNI3 are the cause of cardiomyopathy dilated type 1FF (CMD1FF) [MIM:[https://omim.org/entry/613286 613286]. Dilated cardiomyopathy is a disorder characterized by ventricular dilation and impaired systolic function, resulting in congestive heart failure and arrhythmia. Patients are at risk of premature death.
== Function ==
[https://www.uniprot.org/uniprot/TNNC1_HUMAN TNNC1_HUMAN] Troponin is the central regulatory protein of striated muscle contraction. Tn consists of three components: Tn-I which is the inhibitor of actomyosin ATPase, Tn-T which contains the binding site for tropomyosin and Tn-C. The binding of calcium to Tn-C abolishes the inhibitory action of Tn on actin filaments.[https://www.uniprot.org/uniprot/TNNI3_HUMAN TNNI3_HUMAN] Troponin I is the inhibitory subunit of troponin, the thin filament regulatory complex which confers calcium-sensitivity to striated muscle actomyosin ATPase activity.
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== Publication Abstract from PubMed ==
In cardiac and skeletal muscle, the troponin complex turns muscle contraction on and off in a calcium-dependent manner. Many small molecules are known to bind to the troponin complex to modulate its calcium binding affinity, and this may be useful in a broad range of conditions in which striated muscle function is compromised, such as congestive heart failure. As a tool for developing drugs specific for the cardiac isoform of troponin, we have designed a chimeric construct (cChimera) consisting of the regulatory N-terminal domain of cardiac troponin C (cNTnC) fused to the switch region of cardiac troponin I (cTnI), mimicking the key binding event that turns on muscle contraction. We demonstrate by solution NMR spectroscopy that cChimera faithfully reproduces the native interface between cTnI and cNTnC. We determined that small molecules based on diphenylamine can bind to cChimera with a KD as low as 10muM. Solution NMR structures show that minimal structural perturbations in cChimera are needed to accommodate 3-methyldiphenylamine (3-mDPA), which is probably why it binds with higher affinity than previously studied compounds like bepridil, despite its significantly smaller size. The unsubstituted aromatic ring of 3-mDPA binds to an inner hydrophobic pocket adjacent to the central beta sheet of cNTnC. However, the methyl-substituted ring is able to bind in two different orientations, either inserting into the cNTnC-cTnI interface or "flipping out" to form contacts primarily with helix C of cNTnC. Our work suggests that preservation of the native interaction between cNTnC and cTnI is key to the development of a high affinity cardiac troponin-specific drug.

Structures reveal details of small molecule binding to cardiac troponin.,Cai F, Li MX, Pineda-Sanabria SE, Gelozia S, Lindert S, West F, Sykes BD, Hwang PM J Mol Cell Cardiol. 2016 Dec;101:134-144. doi: 10.1016/j.yjmcc.2016.10.016. Epub , 2016 Nov 5. PMID:27825981<ref>PMID:27825981</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Troponin 3D structures|Troponin 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Cai F]]
[[Category: Hwang PM]]
[[Category: Sykes BD]]