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Eukaryotic Initiation Factor
Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an important input for post-transcription gene regulation. Several initiation factors form a complex with the small 40S ribosomal subunit and Met- tRNAiMet called the 43S preinitiation complex (43S PIC). Additional factors of the eIF4F complex (eIF4A, E, and G) recruit the 43S PIC to the five-prime cap structure of the mRNA, from which the 43S particle scans 5'-->3' along the mRNA to reach an AUG start codon. Recognition of the start codon by the Met-tRNAiMet promotes gated phosphate and eIF1 release to form the 48S preinitiation complex (48S PIC), followed by large 60S ribosomal subunit recruitment to form the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors, reflecting the gre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabolic reactions, DNA replication, Cell signaling, responding to stimuli, providing Cytoskeleton, structure to cells and Fibrous protein, organisms, and Intracellular transport, transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the Nucleic acid sequence, nucleotide sequence of their genes, and which usually results in protein folding into a specific Protein structure, 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A-site
The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other two sites being P-site (peptidyl) and E-site (exit). References Ribosomal RNA {{Genetics-stub ... [...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 Eukaryotic Initiation Factor 2 (eIF2) is a 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 ... 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 under stress conditions, but this result has been debated. References Further reading * * * * * * * * * * * * * * {{gene-3-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DsRNA
Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself ( non-coding RNA) or by forming a template for the production of proteins ( messenger RNA). RNA and deoxyribonucleic acid (DNA) are nucleic acids. The nucleic acids constitute one of the four major macromolecules essential for all known forms of life. RNA is assembled as a chain of nucleotides. Cellular organisms use messenger RNA (mRNA) to convey genetic information (using the nitrogenous bases of guanine, uracil, adenine, and cytosine, denoted by the letters G, U, A, and C) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome. Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function in w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Kinase R
Protein kinase RNA-activated also known as protein kinase R (PKR), interferon-induced, double-stranded RNA-activated protein kinase, or eukaryotic translation initiation factor 2-alpha kinase 2 (EIF2AK2) is an enzyme that in humans is encoded by the ''EIF2AK2'' gene on chromosome 2. PKR is a serine/tyrosine kinase that is 551 amino acids long. PKR is inducible by various mechanisms of stress and protects against viral infections. It also has a role in several signaling pathways. Mechanism of action Protein kinase-R is activated by double-stranded RNA (dsRNA), introduced to the cells by a viral infection. In situations of viral infection, the dsRNA created by viral replication and gene expression binds to the N-terminal domain, activating the protein. PKR activation via dsRNA is length dependent, requiring the dsRNA to be 30 bp in length to bind to PKR molecules. However, excess dsRNA can diminish activation of PKR. Binding to dsRNA is believed to activate PKR by inducing d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reticulocytes
In hematology, reticulocytes are immature red blood cells (RBCs). In the process of erythropoiesis (red blood cell formation), reticulocytes develop and mature in the bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells. Like mature red blood cells, in mammals, reticulocytes do not have a cell nucleus. They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA that becomes visible under a microscope with certain stains such as new methylene blue and Romanowsky stain. Clinical significance To accurately measure reticulocyte counts, automated counters use a combination of laser excitation, detectors and a fluorescent dye that marks RNA and DNA (such as titan yellow or polymethine). Reticulocytes appear slightly bluer than other red cells when looked at with the normal Romanowsky stain. Reticulocytes are also relatively large, a characteristic that is described by the mean cor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guanine Nucleotide Exchange Factor
Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated structural domains have been shown to exhibit guanine nucleotide exchange activity. Some GEFs can activate multiple GTPases while others are specific to a single GTPase. Function Guanine nucleotide exchange factors (GEFs) are proteins or protein domains involved in the activation of small GTPases. Small GTPases act as molecular switches in intracellular signaling pathways and have many downstream targets. The most well-known GTPases comprise the Ras superfamily and are involved in essential cell processes such as cell differentiation and proliferation, cytoskeletal organization, vesicle trafficking, and nuclear transport. GTPases are active when bound to GTP and inactive when bound to GDP, allowing their activity to be regulated by GEFs and th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2B
eIF2B is a protein complex found in eukaryotes. It is the guanine nucleotide exchange factor for the eukaryotic initiation factor 2 and therefore converts the inactive eIF2- GDP to the active eIF2- GTP. This activation is hindered by phosphorylation of the alpha subunit of eIF2, which leads to a stable eIF2α-P-GDP-eIF2B complex and therefore inhibits translation initiation. Human genes which encode eIF-2B proteins include: * EIF2B1 Translation initiation factor eIF-2B subunit alpha is a protein that in humans is encoded by the ''EIF2B1'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of ... – alpha subunit (26kDa) * EIF2B2 – beta subunit (39kDa) * EIF2B3 – gamma subunit (58kDa) * EIF2B4 – delta subunit (67kDa) * EIF2B5 – epsilon subunit (82kDa) References Protein biosynthesis Gene expression Proteins {{enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Signaling
In biology, cell signaling (cell signalling in British English) is the Biological process, process by which a Cell (biology), cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all Cell (biology), cellular life in both prokaryotes and eukaryotes. Typically, the signaling process involves three components: the signal, the receptor, and the effector. In biology, signals are mostly chemical in nature, but can also be physical cues such as pressure, Membrane potential, voltage, temperature, or light. Chemical signals are molecules with the ability to bind and activate a specific Receptor (biochemistry), receptor. These molecules, also referred to as Ligand (biochemistry), ligands, are chemically diverse, including ions (e.g. Na+, K+, Ca2+, etc.), lipids (e.g. steroid, prostaglandin), peptides (e.g. insulin, ACTH), carbohydrates, glycosylated proteins (proteoglycans), nucleic acids, etc. Peptide and lipid ligands are particularly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2S3
Eukaryotic translation initiation factor 2 subunit 3 (eIF2γ) is a protein that in humans is encoded by the ''EIF2S3'' gene. Function Eukaryotic translation initiation factor 2 (eIF2) functions in the early steps of protein synthesis by forming a ternary complex with GTP and initiator tRNA and binding to a 40S ribosomal subunit. eIF2 is composed of three subunits, alpha (α), beta (β), and gamma (γ, this article), with the protein encoded by this gene representing the gamma subunit. See also * eIF2 Eukaryotic Initiation Factor 2 (eIF2) is a 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 ... References Further reading * * * * * * * * * * * * * * * * * {{gene-X-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2S2
Eukaryotic translation initiation factor 2 subunit 2 (eIF2β) is a protein that in humans is encoded by the ''EIF2S2'' gene. Function Eukaryotic translation initiation factor 2 (eIF2) functions in the early steps of protein synthesis by forming a ternary complex with GTP and initiator tRNA and binding to a 40S ribosomal subunit. eIF2 is composed of three subunits, alpha (α), beta (β, this article), and gamma (γ), with the protein encoded by this gene representing the beta subunit. The beta subunit catalyzes the exchange of GDP for GTP, which recycles the eIF2 complex for another round of initiation. Regulation Both eIF2α and eIF2β expression is regulated by the NRF1 transcription factor. See also * eIF2 Eukaryotic Initiation Factor 2 (eIF2) is a 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 ... References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF2S1
Eukaryotic translation initiation factor 2 subunit 1 (eIF2α) is a protein that in humans is encoded by the ''EIF2S1'' gene. Function The protein encoded by this gene is the alpha (α) subunit of the translation initiation factor eIF2 protein complex which catalyzes an early regulated step of protein synthesis initiation, promoting the binding of the initiator tRNA (Met-tRNAiMet) to 40S ribosomal subunits. Binding occurs as a ternary complex of methionyl-tRNA, eIF2, and GTP. eIF2 is composed of 3 nonidentical subunits, alpha (α, 36 kD, this article), beta (β, 38 kD), and gamma (γ, 52 kD). The rate of formation of the ternary complex is modulated by the phosphorylation state of eIF2α. Phosphorylation of eIF2α by EIF-2 kinases plays a key role in regulating the integrated stress response. Clinical significance After reperfusion following brain ischemia, there is inhibition of neuron protein synthesis due to phosphorylation of eIF2α. There is colocalization between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
