Structure of the Regulatory N-domain of Human Cardiac Troponin C in Complex with Human Cardiac Troponin I147–163 and Bepridil

Wang, Xu; Li, Monica X.; Sykes, Brian D.

doi:10.1074/jbc.m203896200

Cited by 79 publications

(168 citation statements)

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“…Many recent studies have tended to focus on the interactions between the domains of TnC and peptides from TnI and TnT and have mapped out the interacting regions in some detail. Structures of complexes between TnC domains and TnI peptides (13)(14)(15)(16)(17) have revealed the nature of these interactions at atomic detail and have been confirmed by the recent x-ray structures of cardiac (5) and skeletal troponin (18).…”

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confidence: 74%

“…The T1 domain of TnT was not included, because it causes aggregation of the complex (24,25), and it does not interact with TnC and TnI (2). We used this complex to measure backbone amide 15 N NMR relaxation times, which give information about the rotational tumbling and internal dynamics of proteins (20). These results have been used to delineate the relative motions of the regulatory and structural domains of TnC in the apo (EGTA/Mg 2ϩ ) and calcium-saturated states.…”

mentioning

confidence: 99%

“…20 and 21). Although many nuclei ( 2 H, 13 C, 15 N, 19 F and 31 P) can be used for relaxation studies, backbone amide 15 N relaxation rates (the longitudinal relaxation time, T 1 , and the transverse relaxation time, T 2 , along with nuclear Overhauser effect) are the most common. These relaxation measurements are typically interpreted using the Lipari-Szabo model-free formalism (22), from which an overall rotational correlation time, an internal correlation time, and an order parameter can be obtained for each N-H N bond vector (23).…”

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confidence: 99%

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Calcium-dependent Changes in the Flexibility of the Regulatory Domain of Troponin C in the Troponin Complex

Blumenschein

Stone

Fletterick³

et al. 2005

Journal of Biological Chemistry

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With the recent advances in structure determination of the troponin complex, it becomes even more important to understand the dynamics of its components and how they are affected by the presence or absence of Ca 2؉ . We used NMR techniques to study the backbone dynamics of skeletal troponin C (TnC) in the complex. Transverse relaxation-optimized spectroscopy pulse sequences and deuteration of TnC were essential to assign most of the TnC residues in the complex. Backbone amide 15 N relaxation times were measured in the presence of Ca 2؉ or EGTA/Mg 2؉ . T 1 relaxation times could not be interpreted precisely, because for a molecule of this size, the longitudinal backbone amide 15 N relaxation rate due to chemical shift anisotropy and dipole-dipole interactions becomes too small, and other relaxation mechanisms become relevant. T 2 relaxation times were of the expected magnitude for a complex of this size, and most of the variation of T 2 times in the presence of Ca 2؉ could be explained by the anisotropy of the complex, suggesting a relatively rigid molecule. The only exception was EF-hand site III and helix F immediately after, which are more flexible than the rest of the molecule. In the presence of EGTA/Mg 2؉ , relaxation times for residues in the C-domain of TnC are very similar to values in the presence of Ca 2؉ , whereas the N-domain becomes more flexible. Taken together with the high flexibility of the linker between the two domains, we concluded that in the absence of Ca 2؉ , the N-domain of TnC moves independently from the rest of the complex.The troponin (Tn) 1 complex is responsible for the regulation of contraction in striated skeletal and cardiac muscles. Although many structural studies have been done of pairwise interactions between components of the complex (for reviews see Refs. 1-4), the details at an atomic level of how the complex works as a whole have not as yet been fully elucidated. Recent determination of the crystal structure of cardiac troponin (5) has revealed an apparently quite flexible complex. This has focused interest on the need for dynamics information on the troponin complex in order to properly interpret the structural data.The three components of Tn, troponins I, C, and T, are responsible for inhibiting muscle contraction in the absence of Ca 2ϩ , sensing the change in intracellular Ca 2ϩ levels, releasing the inhibition in the presence of Ca 2ϩ , and transmitting this information to the other components of muscle thin filaments, respectively (for a recent review see Ref.2). Troponin C (TnC) is a Ca 2ϩ -binding protein containing two domains connected by a linker. The linker is a straight ␣-helix in the crystal structure of isolated TnC (6 -8) but is flexible in solution (9). Each domain contains two EF-hand metal-binding sites, and the helices that flank those sites are named A to D in the N-domain and are named E to H in the C-domain. An extra helix at the N terminus is named N. The sites in the N-domain are Ca 2ϩ -specific and important for the regulation of muscle contract...

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confidence: 74%

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confidence: 99%

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confidence: 99%

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Calcium-dependent Changes in the Flexibility of the Regulatory Domain of Troponin C in the Troponin Complex

Blumenschein

Stone

Fletterick³

et al. 2005

Journal of Biological Chemistry

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“…The fact that both the switch region of cTnI, cTnI [147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163] , and bepridil can induce a structural 'opening' in cNTnC·Ca 2+ by interacting with the hydrophobic patch prompted us to explore whether cTnI 147-163 and bepridil compete for cNTnC·Ca 2+ [58]. Using 2D { 1 H, 15 N} HSQC NMR spectroscopy, we examined the binding of bepridil to cNTnC·Ca 2+ in the absence and presence of cTnI 147-163 and of cTnI [147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163] to cNTnC·Ca 2+ in the absence and presence of bepridil.…”

Section: Bepridilmentioning

confidence: 99%

“…A, cNTnC·apo; B, cNTnC·Ca 2+ ; C, cNTnC·Ca 2+ ·bepridil; D, cNTnC·Ca 2+ ·cTnI 147-163 ; E, cNTnC·Ca 2+ · cTnI 147-163 ·bepridil. The figure was adapted from Wang et al [58]. A proposed mechanism of the effects of levosimendan on the N-domain of cTnC.…”

Section: Perspectivementioning

confidence: 99%

Interaction of cardiac troponin with cardiotonic drugs: A structural perspective

Robertson

Sykes

2008

Biochemical and Biophysical Research Communications

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Over the forty years since its discovery, many studies have focused on understanding the role of troponin as a myofilament based molecular switch in regulating the Ca 2+ -dependent activation of striated muscle contraction. Recently, studies have explored the role of cardiac troponin as a target for cardiotonic agents. These drugs are clinically useful for treating heart failure, a condition in which the heart is no longer able to pump enough blood to other organs. These agents act via a mechanism that modulates the Ca 2+ -sensitivity of troponin; such a mode of action is therapeutically desirable because intracellular Ca 2+ concentration is not perturbed, preserving the regulation of other Ca 2+ -based signaling pathways. This review describes molecular details of the interaction of cardiac troponin with a variety of cardiotonic drugs. We present recent structural work that has identified the docking sites of several cardiotonic drugs in the troponin C -troponin I interface and discuss their relevance in the design of troponin based drugs for the treatment of heart disease.

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TroponinC

Gagn��

2004

Handbook of Metalloproteins

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Regulation of contraction in skeletal and cardiac muscle occurs through calcium binding to the protein troponin C (TnC). The N‐terminal domain of TnC (NTnC) carries out the regulatory role through the binding of calcium ions – two calcium ions in skeletal muscle and one in cardiac muscle. Thirty‐nine sequences of TnC have been sequenced so far. Of the 39 sequences of TnC, 5 have had their three‐dimensional structures determined in various forms by NMR and X‐ray. Available structures include 26 uncomplexed structures in various calcium states, and 13 structures in which cardiac and skeletal TnC is complexed with fragments of troponin I and/or troponin T.

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Structure of the Regulatory N-domain of Human Cardiac Troponin C in Complex with Human Cardiac Troponin I147–163 and Bepridil

Cited by 79 publications

References 49 publications

Calcium-dependent Changes in the Flexibility of the Regulatory Domain of Troponin C in the Troponin Complex

Calcium-dependent Changes in the Flexibility of the Regulatory Domain of Troponin C in the Troponin Complex

Interaction of cardiac troponin with cardiotonic drugs: A structural perspective

TroponinC

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