Unexpected, pervasive, conserved secondary structure in highly charged protein regions

Triandafillou, Catherine G.; Pan, Rosalind; Drummond, David A.; Dinner, Aaron R.

doi:10.1016/j.bpj.2022.11.1846

Cited by 1 publication

(2 citation statements)

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“…While disorder predictors all indicate this region should be disordered, recent work has called into question whether highly-charged blocky sequences truly exist as disordered regions and may instead exist as alpha helices (18,(75)(76)(77). While we cannot extrapolate beyond our data, at least for the troponin-T linker (which contains such a sequence), we see no evidence of helicity or changes in IDR dynamics under the range of conditions measured, a result consistent with structural data obtained under both low and high calcium conditions.…”

Section: Discussionmentioning

confidence: 99%

“…This linker is a hot spot for both VUS and pathogenic cardiomyopathy mutations (12)(13)(14)(15). The linker is highly enriched in charged residues, and computational tools predict that it is likely an intrinsically disordered region (IDR) (16,17); however, this prediction has not been tested experimentally, and recent work has called into question whether highly charged blocky sequences are truly disordered (18). Compared to structured regions, IDRs tend to be more dynamic, exploring a large conformational space, and are thus not well described by traditional structural techniques (19,20).…”

Section: Introductionmentioning

confidence: 99%

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Structural dynamics of the intrinsically disordered linker region of cardiac troponin T

Cubuk,

Greenberg,

Greenberg

et al. 2024

Preprint

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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. Mutations in troponin can cause cardiomyopathies; however, it is still a major challenge for the field to connect how changes in sequence affect troponin’s function. Recent high-resolution structures of the thin filament revealed critical insights into the structure-function relationship of the troponin complex, but there remain large, unresolved segments of troponin, including the troponin-T linker region that is a hotspot for several cardiomyopathy mutations. This unresolved yet functionally-significant linker region has been proposed to be intrinsically disordered, with behaviors that are not well described by traditional structural approaches; however, this proposal has not been experimentally verified. Here, we used a combination of single-molecule Förster resonance energy transfer (FRET), molecular dynamics simulations, and functional reconstitution assays to investigate the troponin-T linker region. We experimentally and computationally show that in the context of both isolated troponin and the fully regulated troponin complex, the linker behaves as a dynamic, intrinsically disordered region. This region undergoes polyampholyte expansion in the presence of high salt and distinct conformational changes during the assembly of the troponin complex. We also examine the ΔE160 hypertrophic cardiomyopathy mutation in the linker, and we demonstrate that this mutation does not affect the conformational dynamics of the linker, rather it allosterically affects interactions with other subunits of the troponin complex, leading to increased molecular contractility. Taken together, our data clearly demonstrate the importance of disorder within the troponin-T linker and provide new insights into the molecular mechanisms controlling the pathogenesis of cardiomyopathies.

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Section: Discussionmentioning

confidence: 99%