New Model for Stacking Monomers in Filamentous Actin from Skeletal Muscles of Oryctolagus cuniculus

Actin polymerization and depolymerization in developing vertebrates

Development is a complex process that occurs throughout the life cycle. F-actin, a major component of the cytoskeleton, is essential for the morphogenesis of tissues and organs during development. F-actin is formed by the polymerization of G-actin, and the dynamic balance of polymerization and depolymerization ensures proper cellular function. Disruption of this balance results in various abnormalities and defects or even embryonic lethality. Here, we reviewed recent findings on the structure of G-actin and F-actin and the polymerization of G-actin to F-actin. We also focused on the functions of actin isoforms and the underlying mechanisms of actin polymerization/depolymerization in cellular and organic morphogenesis during development. This information will extend our understanding of the role of actin polymerization in the physiologic or pathologic processes during development and may open new avenues for developing therapeutics for embryonic developmental abnormalities or tissue regeneration.

Structural and functional analysis of actin point mutations leading to nemaline myopathy to elucidate their role in actin function

In this work, we analyzed 78 mutations in the actin protein that cause the disease nemaline myopathy. We analyzed how these mutations are distributed in important regions of the actin molecule (folding nucleus, core of the filament, amyloidogenic regions, disordered regions, regions involved in interaction with other proteins). It was found that 54 mutations (43 residues) fall into the folding nucleus (Ф ≥ 0.5), 11 mutations (10 residues) into the filament core, 14 mutations into the amyloidogenic regions (11 residues), 14 mutations (9 residues) in the unstructured regions, and 24 mutations (22 residues) in regions involved in interaction with other proteins. It was also found that the occurrence of single mutations G44V, V45F, T68I, P72R, K338I and S350L leads to the appearance of new amyloidogenic regions that are not present in native actin. The largest number of mutations (54 out of 78) occurs in the folding nucleus; these mutations are important for folding and therefore can affect the protein folding rate. We have shown that almost all of the considered mutations are associated with the structural characteristics of the actin molecule, and some of the residues we have considered have several important characteristics.

Bioinformatics Analysis of Actin Molecules: Why Quantity Does Not Translate Into Quality?

It is time to review all the available data and find the distinctive characteristics of actin that make it such an important cell molecule. The presented double-stranded organization of filamentous actin cannot explain the strong polymorphism of actin fibrils. In this work, we performed bioinformatics analysis of a set of 296 amino acid actin sequences from representatives of different classes of the Chordate type. Based on the results of the analysis, the degree of conservatism of the primary structure of this protein in representatives of the Chordate type was determined. In addition, 155 structures of rabbit actin obtained using X-ray diffraction analysis and electron microscopy have been analyzed over the past 30 years. From pairwise alignments and the calculation of root-mean-square deviations (RMSDs) for these structures, it follows that they are very similar to each other without correlation with the structure resolution and the reconstruction method: the RMSDs for 11,781 pairs did not exceed 3 Å. It turned out that in rabbit actin most of the charged amino acid residues are located inside the protein, which is not typical for the protein structure. We found that two of six exon regions correspond to structural subdomains. To test the double-stranded organization of the actin structure, it is necessary to use new approaches and new techniques, taking into account our new data obtained from the structural analysis of actin.