The muscle-relaxing C-terminal peptide from troponin I populates a nascent helix, facilitating binding to tropomyosin with a potent therapeutic effect
Por:
F. HORNOS, H. FENG, B. RIZZUTI, M. PALOMINO-SCHATZLEIN, D. WIECZOREK, J. NEIRA and J. JIN
Publicada:
1 ene 2021
Resumen:
The conserved C-terminal end segment of troponin I (TnI) plays a critical role in regulating muscle relaxation. This function is retained in the isolated C-terminal 27 amino acid peptide (residues 184-210) of human cardiac TnI (HcTnI-C27): When added to skinned muscle fibers, HcTnI-C27 reduces the Ca2+-sensitivity of activated myofibrils and facilitates relaxation without decreasing the maximum force production. However, the underlying mechanism of HcTnI-C27 function is unknown. We studied the conformational preferences of HcTnI-C27 and a myopathic mutant, Arg192His, (HcTnI-C27-H). Both peptides were mainly disordered in aqueous solution with a nascent helix involving residues from Trp191 to Ile195, as shown by NMR analysis and molecular dynamics simulations. The population of nascent helix was smaller in HcTnI-C27-H than in HcTnI-C27, as shown by circular dichroism (CD) titrations. Fluorescence and isothermal titration calorimetry (ITC) showed that both peptides bound tropomyosin (alpha Tm), with a detectably higher affinity (similar to 10 mu M) of HcTnI-C27 than that of HcTnI-C27-H (similar to 15 mu M), consistent with an impaired Ca2+-desensitization effect of the mutant peptide on skinned muscle strips. Upon binding to aTm, HcTnI-C27 acquired a weakly stable helix-like conformation involving residues near Trp191, as shown by transferred nuclear Overhauser effect spectroscopy and hydrogen/deuterium exchange experiments. With the potent Ca2+-desensitization effect of HcTnI-C27 on skinned cardiac muscle from a mouse model of hypertrophic cardiomyopathy, the data support that the C-terminal end domain of TnI can function as an isolated peptide with the intrinsic capacity of binding tropomyosin, providing a promising therapeutic approach to selectively improve diastolic function of the heart.
Filiaciones:
F. HORNOS:
Univ Miguel Hernandez, IDIBE, Alicante, Spain
H. FENG:
Wayne State Univ, Sch Med, Dept Physiol, Detroit, MI 48201 USA
B. RIZZUTI:
Licryl UOS Cosenza, CNR NANOTEC, Cosenza, Italy
Univ Calabria, Dept Phys, CEMIF Cal, Cosenza, Italy
:
Ctr Invest Principe Felipe Valencia, Dept NMR, Valencia, Spain
D. WIECZOREK:
Univ Cincinnati, Coll Med, Dept Mol Genet Biochem & Microbiol, Cinncinnnati, OH USA
J. NEIRA:
Univ Miguel Hernandez, IDIBE, Alicante, Spain
Inst Biocomputac & Fis Sistemas Complejos, Zaragoza, Spain
J. JIN:
Wayne State Univ, Sch Med, Dept Physiol, Detroit, MI 48201 USA
Green Published, gold
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