7JGI

NMR structure of the cNTnC-cTnI chimera bound to A7


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 300 
  • Conformers Submitted: 10 
  • Selection Criteria: structures with the lowest energy 

wwPDB Validation   3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

The Role of Electrostatics in the Mechanism of Cardiac Thin Filament Based Sensitizers.

Cai, F.Robertson, I.M.Kampourakis, T.Klein, B.A.Sykes, B.D.

(2020) ACS Chem Biol 15: 2289-2298

  • DOI: 10.1021/acschembio.0c00519
  • Primary Citation of Related Structures:  
    7JGI

  • PubMed Abstract: 
  • Heart muscle contraction is regulated by calcium binding to cardiac troponin C. This induces troponin I (cTnI) switch region binding to the regulatory domain of troponin C (cNTnC), pulling the cTnI inhibitory region off actin and triggering muscle contraction ...

    Heart muscle contraction is regulated by calcium binding to cardiac troponin C. This induces troponin I (cTnI) switch region binding to the regulatory domain of troponin C (cNTnC), pulling the cTnI inhibitory region off actin and triggering muscle contraction. Small molecules targeting this cNTnC-cTnI interface have potential in the treatment of heart disease. Most of these have an aromatic core which binds to the hydrophobic core of cNTnC, and a polar and often charged 'tail'. The calmodulin antagonist W7 is unique in that it acts as calcium desensitizer. W7 binds to the interface of cNTnC and cTnI switch region and weakens cTnI binding, possibly by electrostatic repulsion between the positively charged terminal amino group of W7 and the positively charged RRVR 144-147 region of cTnI. To evaluate the role of electrostatics, we synthesized A7, where the amino group of W7 was replaced with a carboxyl group. We determined the high-resolution solution NMR structure of A7 bound to a cNTnC-cTnI chimera. The structure shows that A7 does not change the overall conformation of the cNTnC-cTnI interface, and the naphthalene ring of A7 sits in the same hydrophobic pocket as that of W7, but the charged tail takes a different route to the surface of the complex, especially with respect to the position of the switch region of cTnI. We measured the affinities of A7 for cNTnC and the cNTnC-cTnI complex and that of the cTnI switch peptide for the cNTnC-A7 complex. We also compared the binding of W7 and A7 for two cNTnC-cTnI chimeras, differing in the presence or absence of the RRVR region of cTnI. A7 decreased the binding affinity of cTnI to cNTnC substantially less than W7 and bound more tightly to the more positively charged chimera. We tested the effects of W7 and A7 on the force-calcium relation of demembranated rat right ventricular trabeculae and demonstrated that A7 has a much weaker desensitization effect than W7. We also synthesized A6, which has one less methylene group on the hydrocarbon chain than A7. A6 did not affect binding of cTnI switch peptide nor change the calcium sensitivity of ventricular trabeculae. These results suggest that the negative inotropic effect of W7 may result from a combination of electrostatic repulsion and steric hindrance with cTnI.


    Organizational Affiliation

    Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2R3, Canada.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Troponin C, slow skeletal and cardiac muscles,Troponin I, cardiac muscle chimeraA125Homo sapiensMutation(s): 2 
Gene Names: TNNC1TNNCTNNI3
UniProt & NIH Common Fund Data Resources
Find proteins for P19429 (Homo sapiens)
Explore P19429 
Go to UniProtKB:  P19429
PHAROS:  P19429
Find proteins for P63316 (Homo sapiens)
Explore P63316 
Go to UniProtKB:  P63316
PHAROS:  P63316
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
V8Y
Query on V8Y

Download Ideal Coordinates CCD File 
C [auth A]7-{[(5-chloronaphthalen-1-yl)sulfonyl]amino}heptanoic acid
C17 H20 Cl N O4 S
MGDCSPFNRAHLFD-UHFFFAOYSA-N
 Ligand Interaction
CA
Query on CA

Download Ideal Coordinates CCD File 
B [auth A]CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 300 
  • Conformers Submitted: 10 
  • Selection Criteria: structures with the lowest energy 
  • OLDERADO: 7JGI Olderado

Structure Validation

View Full Validation Report



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
Other privateCanadaB.D.S., G-14-0005884

Revision History  (Full details and data files)

  • Version 1.0: 2020-09-02
    Type: Initial release
  • Version 1.1: 2020-10-28
    Changes: Structure summary