In eukaryotes, translation initiation occurs by the cap-dependent mechanism. Each translated mRNA must be pre-bound by the translation initiation factor eIF4E. All isoforms of this factor are combined into one family. The review considers natural diversity of the eIF4E isoforms in different organisms, provides structural information about them, and describes their functional role in the processes, such as oncogenesis, participation in the translation of certain mRNAs under stress, and selective use of the individual isoforms by viruses. In addition, this review briefly describes the mechanism of cap-dependent translation initiation and possible ways to regulate the eIF4E function.

Plant viruses from the Potyviridae family have a significant impact on crop productivity worldwide. We conducted a bioinformatic analysis of the VPg sequences from several members of the Potyviridae family. All analyzed primary structures of VPg contain an invariant arginine, which, according to the model we proposed earlier, is located in the functionally important α1–α2 hairpin of the viral protein and forms a recognition contact during the formation of its complex with the eIF4E host cell. Among the amino acid mutations observed in the sequences of VPg PVY, we separately considered those associated with adaptation to the host plant. Several strain-specific mutations were identified, the functional roles of which are currently unclear. For each of the Potyviridae species considered, a consensus VPg sequence was determined. 3D-models of the corresponding proteins were constructed by de novo molecular modelling using the consensus amino acid sequences. Cross-comparative analysis of the theoretical models and the experimental VPg PVY structure obtained by NMR showed that all these proteins share a high degree of structural homology and contain the conserved arginine within the α1–α2 hairpin. However, the spatial position of this arginine may vary across models, which apparently reflects species-specific differences in the VPg recognition module.

The creation of new proteins by combining natural domains is a commonly used technique in protein engineering. In this work, we have tested the possibilities and limitations of using circular homo-oligomeric Sm-like proteins as a basis for attaching other domains. Attachment to such a stable base should bring target domains together and keep them in the correct mutual orientation. We chose a circular homoheptameric Sm-like protein from Sulfolobus acidocaldarius as a stable backbone and the apical domain of the GroEL chaperone protein as the domain of study. This domain by itself, separated from the rest of the GroEL molecule, does not form an oligomeric ring. In our design, the hyperstable SacSm held the seven ADGroELs together and forced them to oligomerize. The designed hybrid protein was obtained and studied with various physical and chemical methods. Stepwise assembly and self-organization of this protein have been shown. First, the SacSm base was assembled, and then ADGroEL was folded on it. Functional testing showed that the obtained fusion protein was able to bind the same non-native proteins as the full-length GroEL chaperone. It also reduced the aggregation of a number of proteins when they were heated, which confirms its chaperone activity. Thus, the engineering path we chose made it possible to create an efficient thermostable chaperone. The result obtained shows the productivity of the way we chose for the creation and stabilization of oligomeric proteins.

In recent years, the eIF4E protein family has been actively studied as one of the major susceptibility factors for Solanaceae plants in relation to potyvirus infections. This makes eIF4E an attractive target for genome editing to generate resistant varieties. The viral protein VPg interacts with eIF4E family proteins. Measuring the in vitro affinity of VPg for different eIF4E isoforms has traditionally been difficult. The main reason for this is the high aggregation propensity of VPg. To overcome this, we used protein engineering to generate a chimeric construct based on a fluorescent protein. This approach greatly facilitated the measurement of affinity between two proteins using surface plasmon resonance (SPR). Our results confirm that the α1–α2 hairpin of PVY VPg is involved in complex formation with eIF4E. These findings provide new insights into the molecular mechanism of this protein–protein interaction.