BPS2026 – Decoding the molecular and functional consequences of intrinsic disorder in cardiac troponin T

The cardiac troponin complex, composed of troponins I, T, and C, plays a central role in regulating the calcium-dependent interactions between myosin and the thin filament. Genetic variants in cardiac troponin have been associated with cardiomyopathies; however, it remains a challenge to connect genotype and phenotype for troponin mutations. This challenge is compounded by the fact that many of these variants are found in regions of troponin that have been proposed to be intrinsically disordered regions (IDRs), where traditional notions about structure-function relationships do not apply. Our previous work has established that (1) the troponin-T (TnT) linker behaves as a dynamic, intrinsically disordered region (IDR) that undergoes conformational changes during the assembly of the troponin complex, and (2) mutations in the disordered linker can be allosterically coupled to functional changes in thin filament function. Here, we used single-molecule FRET, molecular dynamics simulations, and in vitro reconstitution assays to probe the basic C-terminal region of cTnT which has also been proposed to be an IDR. We hypothesized that this disordered region plays a key role in allosterically coupling the linker region to other troponin subunits. We find that at the molecular level, deletion of residues 284–298 does not significantly alter the conformations or dynamics of the disordered linker; however, we find that interactions with members of the troponin complex are significantly affected. On the functional level, we see changes in molecular contractility in in vitro reconstitution assays, when compared to wild-type, consistent with previous studies. Taken together, our results highlight the importance of IDRs in cTnT for regulating thin-filament function and inter/intra-molecular interactions.