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Published on: May 12, 2023
Crystal structure of the Trypanosoma cruzi EIF4E5 translation factor homologue in complex with mRNA cap-4
Lidia Watanabe Reolon1,2, Sophie Vichier-Guerre3, Bruno Moisés de Matos1,2
1Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ-PR, Curitiba, Paraná 81350-010, Brazil.
Abstract:
Association of the initiation factor eIF4E with the mRNA cap structure is a key step for translation. Trypanosomatids present six eIF4E homologues, showing a low conservation and also differing significantly from the IF4Es of multicellular eukaryotes. On the mRNA side, while in most eukaryotes the mRNA contains cap-0 (7-methyl-GTP), the trypanosomatid mRNA features a cap-4, which is formed by a cap-0, followed by the AACU sequence containing 2'-O-ribose methylations and base methylations on nucleotides 1 and 4. The studies on eIF4E-cap-4 interaction have been hindered by the difficulty to synthesize this rather elaborated cap-4 sequence. To overcome this problem, we applied a liquid-phase oligonucleotide synthesis strategy and describe for the first time the crystal structure of a trypanosomatid eIF4E (T. cruzi EIF4E5) in complex with cap-4. The TcEIF4E5-cap-4 structure allowed a detailed description of the binding mechanism, revealing the interaction mode for the AACU sequence, with the bases packed in a parallel stacking conformation and involved, together with the methyl groups, in hydrophobic contacts with the protein. This binding mechanism evidences a distinct cap interaction mode in comparison with previously described eIF4E structures and may account for the difference of TcEIF4E5-cap-4 dissociation constant in comparison with other eIF4E homologues.
Insights
Trypanosomatid translation initiation factor eIF4E binds mRNA cap-4 differently than other eukaryotes. This study reveals the crystal structure of T. cruzi EIF4E5 complexed with cap-4, detailing a unique hydrophobic interaction mechanism.
Area of Science:
- Molecular Biology
- Structural Biology
- Parasitology
Background:
- Translation initiation factor eIF4E binding to mRNA cap is crucial for protein synthesis.
- Trypanosomatid eIF4E homologues are poorly conserved and differ from those in multicellular eukaryotes.
- Trypanosomatid mRNA possesses a unique cap-4 structure, unlike the common cap-0 found in most eukaryotes.
Purpose of the Study:
- To investigate the interaction between trypanosomatid eIF4E and the unique cap-4 mRNA structure.
- To overcome challenges in synthesizing the complex cap-4 sequence for structural studies.
- To determine the crystal structure of a trypanosomatid eIF4E (T. cruzi EIF4E5) in complex with cap-4.
Main Methods:
- Application of a liquid-phase oligonucleotide synthesis strategy to create the cap-4 structure.
- X-ray crystallography to determine the structure of the T. cruzi EIF4E5-cap-4 complex.
- Detailed analysis of the binding mechanism between TcEIF4E5 and cap-4.
Main Results:
- First description of the crystal structure of a trypanosomatid eIF4E (TcEIF4E5) bound to cap-4.
- Elucidation of the binding mechanism for the AACU sequence within cap-4.
- Identification of parallel base stacking and hydrophobic contacts between TcEIF4E5 and cap-4.
Conclusions:
- The binding mechanism of TcEIF4E5 to cap-4 is distinct from other characterized eIF4E structures.
- Hydrophobic interactions involving methyl groups and bases play a key role in TcEIF4E5-cap-4 binding.
- This unique interaction mode may explain the observed differences in the dissociation constant of TcEIF4E5-cap-4 compared to other eIF4E homologues.
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