Abstract
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.
Highlights
Actin was discovered in 1948 by the Hungarian biochemist Bruno Straub
The amino acid sequence of skeletal and cardiac muscle actin consists of 375 amino acid residues, including one unusual amino acid residue, 3-methylhistidine, which is formed posttranslationally
Bioinformatics analysis of actin showed that: (1) The amino acid sequences of actin in representatives of different classes of chordates are highly conservative; (2) Analysis of exons showed that exon IV corresponds to subdomain 4 and exon V corresponds to subdomain 3; (3) The 3D actin rabbit monomer structures resolved from 1991 to 2020 are very similar: the rootmean-square deviations (RMSDs) for 11,781 pairs does not exceed 3 Å, the RMSD is about zero for monomeric structures in the filamentous actin (2W49 and 1M8Q); (4) Most of the charged amino acid residues are located within actin structure, which is unusual for a protein structure
Summary
Actin was discovered in 1948 by the Hungarian biochemist Bruno Straub. This protein was named for its ability to activate ( actin) ATP hydrolysis catalyzed by myosin. Actin is a muscle tissue protein, the polymerized form of which (F-actin) forms microfilaments—one of the main components of the cytoskeleton of eukaryotic cells. Actin makes up 5–15% of the total cellular protein and is the most important protein in eukaryotic cells (Lodish et al, 2000). Actin analogs have been found in bacteria (Popp et al, 2008, 2010; Galkin et al, 2009) and archaea (Izoré et al, 2014; Braun et al, 2015). Actin monomer (G-actin) is a water-soluble globular structural protein with a molecular weight of 42 kDa, consisting of 375 or 374 amino acid residues. In vertebrates, depending on the isoelectric point, three actin isoforms are distinguished, α, β, and γ (Vandekerckhove and Weber, 1978)
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