Abstract
To date, some scientific evidence (limited proteolysis, mass spectrometry analysis, electron microscopy (EM)) has accumulated, which indicates that the generally accepted model of double-stranded of filamentous actin (F-actin) organization in eukaryotic cells is not the only one. This entails an ambiguous understanding of many of the key cellular processes in which F-actin is involved. For a detailed understanding of the mechanism of F-actin assembly and actin interaction with its partners, it is necessary to take into account the polymorphism of the structural organization of F-actin at the molecular level. Using electron microscopy, limited proteolysis, mass spectrometry, X-ray diffraction, and structural modeling we demonstrated that F-actin presented in the EM images has no double-stranded organization, the regions of protease resistance are accessible for action of proteases in F-actin models. Based on all data, a new spatial model of filamentous actin is proposed, and the F-actin polymorphism is discussed.
Highlights
At present, much attention is being paid to the study of the mechanisms of aggregation of proteins and peptides, especially the elucidation of the organization of their ordered aggregates [1,2,3,4]
In the work of Kudryashov et al [42] the structure of filamentous actin was proposed on the basis of dimeric crystal structures, which were obtained by cross-linking of amino acid residues Q41 and C374 included in two adjacent actin molecules
The existing filamentous actin (F-actin) model cannot be entirely described by a single structural model, since this model cannot explain the destruction of actin filaments after introduction of disulfide bonds [43] between residues which participated in the contacts between monomers in actin filament according to the double-stranded model of F-actin [41,54,55]
Summary
Much attention is being paid to the study of the mechanisms of aggregation of proteins and peptides, especially the elucidation of the organization of their ordered aggregates [1,2,3,4]. In the work of Kudryashov et al [42] the structure of filamentous actin was proposed on the basis of dimeric crystal structures, which were obtained by cross-linking of amino acid residues Q41 and C374 included in two adjacent actin molecules. This model differs from the Holmes ‘s model [41] by the smaller twist of two consecutive actin molecules relative to each other.
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