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Structure of the inhibitor W7 bound to the regulatory domain of cardiac troponin C.

Hoffman RM, Sykes BD - Biochemistry (2009)

Bottom Line: The protein-W7 interface is defined through a three-dimensional {(1)H,(13)C}-edited-{(1)H,(12)C}-detected NOESY NMR experiment, and other aspects of the structure are modeled as perturbations to previously known coordinates and restraints.The structure supports the previously proposed troponin I blocking mechanism for the activity of W7 in striated muscle and suggests a role for the flexible tail of W7 in stabilization of the bound state.This clarifies the structure-activity relationships of W7 and implicates an electrostatically mediated component of activity in common analogues of W7, including the antipsychotic trifluoroperazine and the cardiotonic levosimendan.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.

ABSTRACT
The calmodulin antagonist W7 binds to troponin C in the presence of Ca(2+) and inhibits striated muscle contraction. This study integrates multiple data into the structure of the regulatory domain of human cardiac troponin C (cNTnC) bound to Ca(2+) and W7. The protein-W7 interface is defined through a three-dimensional {(1)H,(13)C}-edited-{(1)H,(12)C}-detected NOESY NMR experiment, and other aspects of the structure are modeled as perturbations to previously known coordinates and restraints. The structure determination protocol optimizes the protein-W7 contacts prior to the introduction of protein-W7 steric interactions or conformational changes in the protein. The structure determination protocol gives families of conformers that all have an optimal docking as assessed by satisfaction of the target function. The structure supports the previously proposed troponin I blocking mechanism for the activity of W7 in striated muscle and suggests a role for the flexible tail of W7 in stabilization of the bound state. This clarifies the structure-activity relationships of W7 and implicates an electrostatically mediated component of activity in common analogues of W7, including the antipsychotic trifluoroperazine and the cardiotonic levosimendan.

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Related in: MedlinePlus

Ten lowest-energy conformers (best 20%) from the plainQ calculation. Depictions are as in Figure 6, but the Ca2+ ions are also shown, as gray spheres. The non-carbon atoms of W7 are colored gray; hydrogens are not shown. (A) The N-terminal helix (helix N) of cNTnC is at the top of the figure pointing to the left and down. Helix D is pointing out of the page. (B) A different orientation of the same ensemble. Helices A and B are closest to the reader.
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fig7: Ten lowest-energy conformers (best 20%) from the plainQ calculation. Depictions are as in Figure 6, but the Ca2+ ions are also shown, as gray spheres. The non-carbon atoms of W7 are colored gray; hydrogens are not shown. (A) The N-terminal helix (helix N) of cNTnC is at the top of the figure pointing to the left and down. Helix D is pointing out of the page. (B) A different orientation of the same ensemble. Helices A and B are closest to the reader.

Mentions: The 50 structures vary in the residual energy in the docking term, from 0.017 to 0.175 kcal/mol; 46 of the 50 calculated structures had no violations in the docking term (the other four structures had a single violation.) As shown in Figure 6, the entire ensemble positions W7 similarly, with the only remaining point of convergence being the details of the pose. Considering the 10 best solutions (lowest energies overall), a single pose is favored with a defined conformation for W7’s tail (Figure 7). None of these structures have violations in the docking term, although they do have other inadequacies.


Structure of the inhibitor W7 bound to the regulatory domain of cardiac troponin C.

Hoffman RM, Sykes BD - Biochemistry (2009)

Ten lowest-energy conformers (best 20%) from the plainQ calculation. Depictions are as in Figure 6, but the Ca2+ ions are also shown, as gray spheres. The non-carbon atoms of W7 are colored gray; hydrogens are not shown. (A) The N-terminal helix (helix N) of cNTnC is at the top of the figure pointing to the left and down. Helix D is pointing out of the page. (B) A different orientation of the same ensemble. Helices A and B are closest to the reader.
© Copyright Policy - open-access - ccc-price
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2697600&req=5

fig7: Ten lowest-energy conformers (best 20%) from the plainQ calculation. Depictions are as in Figure 6, but the Ca2+ ions are also shown, as gray spheres. The non-carbon atoms of W7 are colored gray; hydrogens are not shown. (A) The N-terminal helix (helix N) of cNTnC is at the top of the figure pointing to the left and down. Helix D is pointing out of the page. (B) A different orientation of the same ensemble. Helices A and B are closest to the reader.
Mentions: The 50 structures vary in the residual energy in the docking term, from 0.017 to 0.175 kcal/mol; 46 of the 50 calculated structures had no violations in the docking term (the other four structures had a single violation.) As shown in Figure 6, the entire ensemble positions W7 similarly, with the only remaining point of convergence being the details of the pose. Considering the 10 best solutions (lowest energies overall), a single pose is favored with a defined conformation for W7’s tail (Figure 7). None of these structures have violations in the docking term, although they do have other inadequacies.

Bottom Line: The protein-W7 interface is defined through a three-dimensional {(1)H,(13)C}-edited-{(1)H,(12)C}-detected NOESY NMR experiment, and other aspects of the structure are modeled as perturbations to previously known coordinates and restraints.The structure supports the previously proposed troponin I blocking mechanism for the activity of W7 in striated muscle and suggests a role for the flexible tail of W7 in stabilization of the bound state.This clarifies the structure-activity relationships of W7 and implicates an electrostatically mediated component of activity in common analogues of W7, including the antipsychotic trifluoroperazine and the cardiotonic levosimendan.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.

ABSTRACT
The calmodulin antagonist W7 binds to troponin C in the presence of Ca(2+) and inhibits striated muscle contraction. This study integrates multiple data into the structure of the regulatory domain of human cardiac troponin C (cNTnC) bound to Ca(2+) and W7. The protein-W7 interface is defined through a three-dimensional {(1)H,(13)C}-edited-{(1)H,(12)C}-detected NOESY NMR experiment, and other aspects of the structure are modeled as perturbations to previously known coordinates and restraints. The structure determination protocol optimizes the protein-W7 contacts prior to the introduction of protein-W7 steric interactions or conformational changes in the protein. The structure determination protocol gives families of conformers that all have an optimal docking as assessed by satisfaction of the target function. The structure supports the previously proposed troponin I blocking mechanism for the activity of W7 in striated muscle and suggests a role for the flexible tail of W7 in stabilization of the bound state. This clarifies the structure-activity relationships of W7 and implicates an electrostatically mediated component of activity in common analogues of W7, including the antipsychotic trifluoroperazine and the cardiotonic levosimendan.

Show MeSH
Related in: MedlinePlus