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1.
Nat Commun ; 15(1): 6010, 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-39019880

RESUMO

The conformational dynamics of single-stranded nucleic acids are fundamental for nucleic acid folding and function. However, their elementary chain dynamics have been difficult to resolve experimentally. Here we employ a combination of single-molecule Förster resonance energy transfer, nanosecond fluorescence correlation spectroscopy, and nanophotonic enhancement to determine the conformational ensembles and rapid chain dynamics of short single-stranded nucleic acids in solution. To interpret the experimental results in terms of end-to-end distance dynamics, we utilize the hierarchical chain growth approach, simple polymer models, and refinement with Bayesian inference to generate structural ensembles that closely align with the experimental data. The resulting chain reconfiguration times are exceedingly rapid, in the 10-ns range. Solvent viscosity-dependent measurements indicate that these dynamics of single-stranded nucleic acids exhibit negligible internal friction and are thus dominated by solvent friction. Our results provide a detailed view of the conformational distributions and rapid dynamics of single-stranded nucleic acids.


Assuntos
DNA de Cadeia Simples , Transferência Ressonante de Energia de Fluorescência , Conformação de Ácido Nucleico , DNA de Cadeia Simples/química , Teorema de Bayes , Espectrometria de Fluorescência , Viscosidade , Solventes/química , Modelos Moleculares
2.
Curr Opin Cell Biol ; 89: 102375, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38850681

RESUMO

Intermediate filaments (IFs) are integral to the cell cytoskeleton, supporting cellular mechanical stability. Unlike other cytoskeletal components, the detailed structure of assembled IFs has yet to be resolved. This review highlights new insights, linking the complex IF hierarchical assembly to their mechanical properties and impact on cellular functions. While we focus on vimentin IFs, we draw comparisons to keratins, showcasing the distinctive structural and mechanical features that underlie their unique mechanical responses.


Assuntos
Filamentos Intermediários , Filamentos Intermediários/metabolismo , Filamentos Intermediários/química , Humanos , Animais , Fenômenos Biomecânicos , Citoesqueleto/metabolismo , Citoesqueleto/química , Vimentina/metabolismo , Vimentina/química , Queratinas/química , Queratinas/metabolismo
3.
Nat Struct Mol Biol ; 31(6): 939-949, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38632361

RESUMO

Intermediate filaments (IFs) are integral components of the cytoskeleton. They provide cells with tissue-specific mechanical properties and are involved in numerous cellular processes. Due to their intricate architecture, a 3D structure of IFs has remained elusive. Here we use cryo-focused ion-beam milling, cryo-electron microscopy and tomography to obtain a 3D structure of vimentin IFs (VIFs). VIFs assemble into a modular, intertwined and flexible helical structure of 40 α-helices in cross-section, organized into five protofibrils. Surprisingly, the intrinsically disordered head domains form a fiber in the lumen of VIFs, while the intrinsically disordered tails form lateral connections between the protofibrils. Our findings demonstrate how protein domains of low sequence complexity can complement well-folded protein domains to construct a biopolymer with striking mechanical strength and stretchability.


Assuntos
Microscopia Crioeletrônica , Filamentos Intermediários , Vimentina , Vimentina/química , Vimentina/metabolismo , Vimentina/ultraestrutura , Filamentos Intermediários/química , Filamentos Intermediários/metabolismo , Filamentos Intermediários/ultraestrutura , Humanos , Modelos Moleculares , Domínios Proteicos , Conformação Proteica em alfa-Hélice
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