1LXF

Structure of the Regulatory N-domain of Human Cardiac Troponin C in Complex with Human Cardiac Troponin-I(147-163) and Bepridil

Summary for 1LXF

• Entry DOI: 10.2210/pdb1lxf/pdb
• NMR Information: BMRB: 5386
• Descriptor: TROPONIN C, SLOW SKELETAL AND CARDIAC MUSCLES, Troponin I, cardiac muscle, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: muscle, cardiac troponin c-drug interaction, bepridil, cardiac troponin i-drug interaction, metal binding protein, protein binding
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 2
• Total formula weight: 12283.11

Authors

Wang, X.,Li, M.X.,Sykes, B.D. (deposition date: 2002-06-05, release date: 2002-12-11, Last modification date: 2024-05-22)

Primary citation

Wang, X.,Li, M.X.,Sykes, B.D.
Structure of the regulatory N-domain of human cardiac troponin C in complex with human cardiac troponin I147-163 and bepridil.
J.Biol.Chem., 277:31124-31133, 2002

PubMed Abstract: Cardiac troponin C (cTnC) is the Ca(2+)-dependent switch for contraction in heart muscle and a potential target for drugs in the therapy of heart failure. Ca(2+) binding to the regulatory domain of cTnC (cNTnC) induces little structural change but sets the stage for cTnI binding. A large "closed" to "open" conformational transition occurs in the regulatory domain upon binding cTnI(147-163) or bepridil. This raises the question of whether cTnI(147-163) and bepridil compete for cNTnC.Ca(2+). In this work, we used two-dimensional (1)H,(15)N-heteronuclear single quantum coherence (HSQC) NMR spectroscopy to examine the binding of bepridil to cNTnC.Ca(2+) in the absence and presence of cTnI(147-163) and of cTnI(147-163) to cNTnC.Ca(2+) in the absence and presence of bepridil. The results show that bepridil and cTnI(147-163) bind cNTnC.Ca(2+) simultaneously but with negative cooperativity. The affinity of cTnI(147-163) for cNTnC.Ca(2+) is reduced approximately 3.5-fold by bepridil and vice versa. Using multinuclear and multidimensional NMR spectroscopy, we have determined the structure of the cNTnC.Ca(2+).cTnI(147-163).bepridil ternary complex. The structure reveals a binding site for cTnI(147-163) primarily located on the A/B interhelical interface and a binding site for bepridil in the hydrophobic pocket of cNTnC.Ca(2+). In the structure, the N terminus of the peptide clashes with part of the bepridil molecule, which explains the negative cooperativity between cTnI(147-163) and bepridil for cNTnC.Ca(2+). This structure provides insights into the features that are important for the design of cTnC-specific cardiotonic drugs, which may be used to modulate the Ca(2+) sensitivity of the myofilaments in heart muscle contraction.

PubMed: 12060657
DOI: 10.1074/jbc.M203896200

Experimental method

SOLUTION NMR