The process of muscle contraction is regulated in a calcium-dependent manner by the structural movements of the polymeric tropomyosin/troponin complex across actin thin filaments to regulate myosin binding and subsequent force generation. The protein troponin T plays structural roles as both a scaffold for the troponin complex and an anchor of the complex to the head-to-tail overlap domain of tropomyosin via interactions with its TnT1 domain. Patient-derived mutations in the TnT1 and tropomyosin overlap domains can disrupt regulation that may lead to various cardiomyopathies such as hypertrophic cardiomyopathy or dilated cardiomyopathy over time. Early detection of cardiomyopathy-causing mutations through genetic screening and predictive modeling will allow for early therapeutic intervention and possible avoidance of later pathological cardiac remodeling. A screening method based on energy minimization calculations has been developed to identify possible TnT1 mutations which affect the TnT1-tropomyosin interface to predict potential outcomes of the mutations on regulatory function. The list of ∼1100 troponin and tropomyosin point mutations generated included clinically relevant mutations as well as unreported single nucleotide changes that may yet arise in the patient population. Outlier mutations were classified as having an electrostatic interaction energy value differing significantly from the wild type. Four of these outlier mutations, R130C in troponin T and E250V, E250K, and E257K in tropomyosin, were further explored using molecular dynamics to verify their potential impact on thin filament structure, in particular the salt bridge formed by these residues in the wild type. Of the four, R130C and E257K showed significant deviations from the wild type electrostatic interaction energy values as well as clear structural effects evident from clustering analyses. These two mutants are good candidates for further testing in biochemical and cellular assays to directly assess their impact on cardiac function.
Hamid et al. (Sun,) studied this question.