RNA helicase EIF4A
| RNA helicase EIF4A | ||
|---|---|---|
|
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| Complex of two subunits EIF4A1 and PDCD4 (cyan), one EIF4A1 as a surface model (pink), the other as a ribbon model, according to PDB 2ZU6 | ||
| Mass / length primary structure | 406-411 amino acids | |
| Secondary to quaternary structure | Dimer | |
| Identifier | ||
| Gene name (s) | EIF4A1 , EIF4A2 | |
| Enzyme classification | ||
| EC, category | 3.6.1. , Helicase | |
| Response type | Dissolving hydrogen bonds and unwinding dsNA | |
| Substrate | ATP + double stranded RNA | |
| Products | ADP + phosphate + single stranded RNA | |
| Occurrence | ||
| Parent taxon | Eukaryotes , some bacteria | |
eIF4A ( e ukaryotischer I nitiations f actuator 4A ) refers to a group of proteins involved in the translation of mRNA involved in protein. They belong to the initiation factors . The translation and thus the synthesis of proteins in the cell is controlled by the amount of eIF4A present.
The eIF4A act as a helicase to unwind the mRNA to be translated and as an ATPase . The energy required for this process is obtained from the hydrolysis of ATP . The unwinding enables the ribosomes to attach to the mRNA.
However, the translation is not always equally dependent on the activity of eIF4A, since eIF4A requires the 5'-cap structure typical of eukaryotic mRNA to form the initiation complex . If a CAP-independent initiation mechanism is used by an mRNA (e.g. through an internal ribosomal entry point, IRES ), the eIF4A binding to the IRES is no longer the decisive step for binding to the ribosomes and thus the translation is no longer over regulates the initiation complex. This CAP-independent translation is used by a few cellular genes (e.g. the oncogene c-myc or ornithine decarboxylase ) and some viruses (e.g. hepatitis C virus or picornaviruses such as poliovirus ). In addition, viral proteins of the poliovirus are able to cleave the eIF4 G and thereby prevent the translation of the cellular mRNAs.
An inhibitor of the activity of eIF4A is the coral - steroid Hippuristanol .Weiterhin is eIF4A by the natural product Silvestrol inhibited.
Individual evidence
Web links
- reactome: Formation of the cap-binding eIF4F complex
- reactome: Cap-bound mRNA is activated by helicases
- reactome: eIF2: GTP is hydrolyzed, eIFs are released