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Hepatitis C Virus Internal Ribosome Entry Site
The Hepatitis C virus internal ribosome entry site, or HCV IRES, is an RNA structure within the 5'UTR of the HCV genome that mediates cap-independent translation initiation. Protein translation of most eukaryotic mRNAs occurs by a cap-dependent mechanism and requires association of Met-tRNAiMet, several eukaryotic initiation factors, and GTP with the 40S ribosomal subunit, recruitment to the 5' cap, and scanning along the 5' UTR to reach to start codon. In contrast, translation of hepatitis C virus (HCV) mRNA is initiated by a different mechanism from the usual 5' cap-binding model. This alternate mechanism relies on the direct binding of the 40S ribosomal subunit by the internal ribosome entry site (IRES) in the 5' UTR of HCV RNA. The HCV IRES adopts a complex structure, and may differ significantly from IRES elements identified in picornaviruses. A small number of eukaryotic mRNA have been shown to be translated by internal ribosome entry. IRES structure Nucleotides 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Structure
Protein secondary structure is the three dimensional conformational isomerism, form of ''local segments'' of proteins. The two most common Protein structure#Secondary structure, secondary structural elements are alpha helix, alpha helices and beta sheets, though beta turns and omega loops occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein protein folding, folds into its three dimensional protein tertiary structure, tertiary structure. Secondary structure is formally defined by the pattern of hydrogen bonds between the Amine, amino hydrogen and carboxyl oxygen atoms in the peptide backbone chain, backbone. Secondary structure may alternatively be defined based on the regular pattern of backbone Dihedral angle#Dihedral angles of proteins, dihedral angles in a particular region of the Ramachandran plot regardless of whether it has the correct hydrogen bonds. The concept of secondary structure was first introduced by Kaj Ulrik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picornavirus
Picornaviruses are a group of related nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, positive-sense, single-stranded RNA viruses with a 30 nm icosahedral capsid. The viruses in this family can cause a range of diseases including the common cold, poliomyelitis, meningitis, hepatitis, and paralysis. Picornaviruses constitute the family ''Picornaviridae'', order ''Picornavirales'', and realm '' Riboviria''. There are 158 species in this family, assigned to 68 genera. Notable examples are genera ''Enterovirus'' (including ''Rhinovirus'' and ''Poliovirus''), '' Aphthovirus'', ''Cardiovirus'', and ''Hepatovirus''. Etymology The name "picornavirus" has a dual etymology. Firstly, the name derives from ''picorna''- which is an acronym for "''p''oliovirus, ''i''nsensitivity to ether, ''c''oxsackievirus, ''o''rphan virus, ''r''hinovirus, and ribo''n''ucleic ''a''cid". Secondly, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prokaryotic Initiation Factor-2
Bacterial initiation factor-2 is a bacterial initiation factor. IF2 binds to an initiator tRNA and controls the entry of tRNA onto the ribosome. IF2, bound to GTP, binds to the 30S P site. After associating with the 30S subunit, fMet-tRNAf binds to the IF2 then IF2 transfers the tRNA into the partial P site. When the 50S subunit joins, it hydrolyzes GTP to GDP and Pi, causing a conformational change in the IF2 that causes IF2 to release and allow the 70S ribosome to form. Human mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ... use a nuclear-encoded homolog, MTIF2, for translation initiation. References {{GTPases Molecular biology Protein biosynthesis Gene expression ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF5B
Eukaryotic translation initiation factor 5B is a protein that in humans is encoded by the ''EIF5B'' gene. Accurate initiation of translation in eukaryotes is complex and requires many factors, some of which are composed of multiple subunits. The process is simpler in bacteria which have only three initiation factors (IF1, IF2, IF3). Two of these factors are conserved in eukaryotes: the homolog of IF1 is eIF1A and the homolog of IF2 is eIF5B. This gene encodes eIF5B. Factors eIF1A and eIF5B interact on the ribosome along with other initiation factors and GTP to position the initiation methionine tRNA on the start codon of the mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is ... so that translation initiates accurately. References Further reading * * * * * * * * * * * * * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LGTN
Ligatin, otherwise known as eIF2D, is a protein that in humans is encoded by the ''LGTN'' gene. This protein is not a component of the heterotrimeric eIF2 complex, but instead functions in different pathways of eukaryotic translation. Function This gene encodes a protein receptor that localizes phosphoglycoproteins within endosomes and at the cell periphery. This trafficking receptor for phosphoglycoproteins may play a role in neuroplasticity by modulating cell-cell interactions, intracellular adhesion, and protein binding at membrane surfaces. In hippocampal neurons, long-lasting down-regulation of ligation mRNA levels occurs via post-transcriptional RNA processing following glutamate receptor activation. This protein contains single PUA and SUI1 domains and these domains may function in RNA binding and translation initiation, respectively. See also *Eukaryotic translation *Eukaryotic initiation factor Eukaryotic initiation factors (eIFs) are Protein, proteins or Protein c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2A
Eukaryotic translation initiation factor 2A (eIF2A) is a protein that in humans is encoded by the ''EIF2A'' gene. The eIF2A protein is not to be confused with eIF2α, a subunit of the heterotrimeric eIF2 complex. Instead, eIF2A functions by a separate mechanism in eukaryotic translation. Function eIF2A is a 65 kDa protein that catalyzes the formation of puromycin-sensitive 80S preinitiation complexes (Zoll et al., 2002). upplied by OMIMref name="entrez"> It may be important for translation initiation mediated by the HCV IRES The Hepatitis C virus internal ribosome entry site, or HCV IRES, is an RNA structure within the 5'UTR of the HCV genome that mediates cap-independent translation initiation. Protein translation of most eukaryotic mRNAs occurs by a cap-dependen ... under stress conditions, but this result has been debated. References Further reading * * * * * * * * * * * * * * {{gene-3-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2
Eukaryotic Initiation Factor 2 (eIF2) is an eukaryotic initiation factor. It is required for most forms of eukaryotic translation initiation. eIF2 mediates the binding of tRNAiMet to the ribosome in a GTP-dependent manner. eIF2 is a heterotrimer consisting of an alpha (also called subunit 1, EIF2S1), a beta (subunit 2, EIF2S2), and a gamma (subunit 3, EIF2S3) subunit. Once the initiation phase has completed, eIF2 is released from the ribosome bound to GDP as an inactive binary complex. To participate in another round of translation initiation, this GDP must be exchanged for GTP. Function eIF2 is an essential factor for protein synthesis that forms a ternary complex (TC) with GTP and the initiator Met-tRNAiMet. After its formation, the TC binds the 40S ribosomal subunit to form the 43S preinitiation complex (43S PIC). 43S PIC assembly is believed to be stimulated by the initiation factors eIF1, eIF1A, and the eIF3 complex according to ''in vitro'' experiments. The 43S PIC then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4B
Eukaryotic translation initiation factor 4B is a protein that in humans is encoded by the ''EIF4B'' gene. Interactions eIF4B has been shown to interact with and stimulate the activity of eIF4A and bind to the eIF3 complex through the eIF3A subunit. This interaction results in the recruitment of the eukaryotic small ribosomal subunit (40S) to the mRNA which will in turn set the stage for the later steps leading to elongation. See also *Eukaryotic translation *eIF4F Eukaryotic initiation factor 4F (eIF4F) is a heterotrimeric protein complex that binds the 5' cap of messenger RNAs (mRNAs) to promote eukaryotic translation initiation. The eIF4F complex is composed of three non-identical subunits: the DEAD- ... References Further reading * * * * * * * * * * * * * * * * * * {{gene-12-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4G
Eukaryotic translation initiation factor 4 G (eIF4G) is a protein involved in eukaryotic translation initiation and is a component of the eIF4F cap-binding complex. Orthologs of eIF4G have been studied in multiple species, including humans, yeast, and wheat. However, eIF4G is exclusively found in domain Eukarya, and not in domains Bacteria or Archaea, which do not have capped mRNA. As such, eIF4G structure and function may vary between species, although the human EIF4G1 has been the focus of extensive studies. (Other human paralogs are EIF4G2 and EIF4G3.) Across species, eIF4G strongly associates with eIF4E, the protein that directly binds the mRNA cap. Together with the RNA helicase protein eIF4A, these form the eIF4F complex. Within the cell eIF4G is found primarily in the cytoplasm, usually bound to eIF4E; however, it is also found in the nucleus, where its function is unknown. It may have a role in nonsense-mediated decay. History eIF4G stands for eukaryotic initiation fac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4E
Eukaryotic translation initiation factor 4E, also known as eIF4E, is a protein that in humans is encoded by the ''EIF4E'' gene. Structure and function Most eukaryotic cellular mRNAs are blocked at their 5'-ends with the 7-methyl-guanosine five-prime cap structure, m7GpppX (where X is any nucleotide). This structure is involved in several cellular processes including enhanced translational efficiency, splicing, mRNA stability, and RNA nuclear export. eIF4E is a eukaryotic translation initiation factor involved in directing ribosomes to the cap structure of mRNAs. It is a 24-kD polypeptide that exists as both a free form and as part of the eIF4F pre-initiation complex. Almost all cellular mRNA require eIF4E in order to be translated into protein. The eIF4E polypeptide is the rate-limiting component of the eukaryotic translation apparatus and is involved in the mRNA-ribosome binding step of eukaryotic protein synthesis. The other subunits of eIF4F are a 47-kD polypeptide, terme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF4A
The eukaryotic initiation factor-4A (eIF4A) family consists of 3 closely related proteins EIF4A1, EIF4A2, and EIF4A3. These factors are required for the binding of mRNA to 40S ribosomal subunits. In addition these proteins are helicases that function to unwind double-stranded RNA. Background The mechanisms governing the basic subsistence of eukaryotic cells are immensely complex; it is therefore unsurprising that regulation occurs at a number of stages of protein synthesis – the regulation of translation has become a well-studied field. Human translational control is of increasing research interest as it has connotations in a range of diseases. Orthologs of many of the factors involved in human translation are shared by a range of eukaryotic organisms; some of which are used as model systems for the investigation of translation initiation and elongation, for example: sea urchin eggs upon fertilization, rodent brain and rabbit reticulocytes. Monod and Jacob were among the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF1AX
Eukaryotic translation initiation factor 1A, X-chromosomal (eIF1A) is a protein that in humans is encoded by the ''EIF1AX'' gene. This gene encodes an essential eukaryotic translation initiation factor. The protein is a component of the 43S pre-initiation complex (PIC), which mediates the recruitment of the small 40S ribosomal subunit to the 5' cap of messenger RNAs. Function eIF1A is a small protein (17 kDa in budding yeast) and a component of the 43S preinitiation complexes (PIC). eIF1A binds near the ribosomal A-site, in a manner similar to the functionally related bacterial counterpart IF1. Clinical significance Mutations in this gene have been recurrently seen associated to cases of uveal melanoma with disomy 3. eIF1A is mutated in thyroid cancers. Interactions EIF1AX has been shown to interact with IPO13. See also * Eukaryotic initiation factors Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryoti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
