The muscle-relaxing C-terminal peptide from troponin I populates a nascent helix, facilitating binding to tropomyosin with a potent therapeutic effect

Hornos, Felipe ; Feng, Han-Zhong ; Rizzuti, Bruno ; Palomino-Schätzlein, Martina ; Wieczorek, David ; Neira, José L. ; Jin, J.-P.

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 HcTnIC27-H than in HcTnI-C27, as shown by circular dichroism (CD) titrations. Fluorescence and isothermal titration calorimetry (ITC) showed that both peptides bound tropomyosin (aTm), with a detectably higher affinity (~10 µM) of HcTnIC27 than that of HcTnI-C27-H (~15 µM), 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.

Idioma: Inglés

DOI: 10.1074/jbc.RA120.016012

Año: 2021

Publicado en: Journal of Biological Chemistry 296 (2021), 100228 [18 pp.]
ISSN: 0021-9258

Factor impacto JCR: 5.485 (2021)

Categ. JCR: BIOCHEMISTRY & MOLECULAR BIOLOGY rank: 94 / 297 = 0.316 (2021) - Q2 - T1

Factor impacto CITESCORE: 8.8 - Biochemistry, Genetics and Molecular Biology (Q1)

Factor impacto SCIMAGO: 1.871 - Cell Biology (Q1) - Biochemistry (Q1)

Tipo y forma: Article (Published version)