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40S
The eukaryotic small ribosomal subunit (40S) is the smaller subunit of the eukaryotic 80S ribosomes, with the other major component being the large ribosomal subunit (60S). The "40S" and "60S" names originate from the convention that ribosomal particles are denoted according to their sedimentation coefficients in Svedberg units. It is structurally and functionally related to the 30S subunit of 70S prokaryotic ribosomes. However, the 40S subunit is much larger than the prokaryotic 30S subunit and contains many additional protein segments, as well as rRNA expansion segments. Function The 40S subunit contains the decoding center which monitors the complementarity of tRNA and mRNA in protein translation. It is the largest component of several translation initiation complexes, including the 43S and 48S preinitiation complexes (PICs), being bound by several eukaryotic initiation factors, including eIF1, eIF1A, and eIF3. The 40S ribosomal subunit is also tightly bound by the HCV ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic Ribosome (80S)
Ribosomes are a large and complex molecular machine that catalyzes the synthesis of proteins, referred to as translation. The ribosome selects aminoacylated transfer RNAs (tRNAs) based on the sequence of a protein-encoding messenger RNA (mRNA) and covalently links the amino acids into a polypeptide chain. Ribosomes from all organisms share a highly conserved catalytic center. However, the ribosomes of eukaryotes (animals, plants, fungi, and large number unicellular organisms all with a nucleus) are much larger than prokaryotic (bacterial and archaeal) ribosomes and subject to more complex regulation and biogenesis pathways. Eukaryotic ribosomes are also known as 80S ribosomes, referring to their sedimentation coefficients in Svedberg units, because they sediment faster than the prokaryotic (70S) ribosomes. Eukaryotic ribosomes have two unequal subunits, designated small subunit (40S) and large subunit (60S) according to their sedimentation coefficients. Both subunits contain do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosome
Ribosomes () are molecular machine, macromolecular machines, found within all cell (biology), cells, that perform Translation (biology), biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains. Ribosomes consist of two major components: the small and large ribosomal subunits. Each subunit consists of one or more ribosomal RNA molecules and many ribosomal proteins (). The ribosomes and associated molecules are also known as the ''translational apparatus''. Overview The sequence of DNA that encodes the sequence of the amino acids in a protein is transcribed into a messenger RNA (mRNA) chain. Ribosomes bind to the messenger RNA molecules and use the RNA's sequence of nucleotides to determine the sequence of amino acids needed to generate a protein. Amino acids are selected and carried to the ribosome by transfer RNA (tRNA) molecules, which enter the riboso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic Initiation Factors
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 greater bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPS5 (gene)
40S ribosomal protein S5 is a ribosomal subunit of the Eukaryotic ribosome (80S) complex. In humans it is encoded by the ''RPS5'' gene. Ribosomes, the organelles that catalyze protein synthesis, in ''eukaryotes'', consist of a small 40S subunit and a large 60S subunit (whereas prokaryotic ribosomes are 70 Svedberg units, composed of 50S and 30S The prokaryotic small ribosomal subunit, or 30Svedberg, S subunit, is the smaller subunit of the 70S ribosome found in prokaryotes. It is a complex of the 16S ribosomal RNA (rRNA) and 19 proteins. This complex is implicated in the binding of tr ... subunits). They are located in the cytoplasm. Together these subunits are composed of four RNA species and approximately 80 structurally distinct proteins. This gene encodes a ribosomal protein that is a component of the eukaryotic 40S subunit. The protein belongs to the S7P family of ribosomal proteins. Variable expression of this gene in colorectal cancers compared to adjacent normal t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EIF3
Eukaryotic initiation factor 3 (eIF3) is a multiprotein complex that functions during the initiation phase of eukaryotic translation. It is essential for most forms of Eukaryotic translation#Cap-dependent initiation, cap-dependent and Eukaryotic translation#cap-independent, cap-independent translation initiation. In humans, eIF3 consists of 13 nonidentical subunits (eIF3a-m) with a combined molecular weight of ~800 kDa, making it the largest Eukaryotic initiation factor, translation initiation factor. The eIF3 complex is broadly conserved across eukaryotes, but the conservation of individual subunits varies across organisms. For instance, while most mammalian eIF3 complexes are composed of 13 subunits, Saccharomyces cerevisiae, budding yeast's eIF3 has only six subunits (eIF3a, b, c, g, i, j). Function eIF3 stimulates nearly all steps of translation initiation. eIF3 also appears to participate in other phases of translation, such as recycling, where it promotes the splitting of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPS2 (gene)
The RPS2 gene is the gene which, in humans, encodes the ''40S ribosomal protein S2''. Ribosomes, the organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins. This gene encodes a ribosomal protein that is a component of the 40S subunit. The protein belongs to the S5P family of ribosomal proteins. It is located in the cytoplasm. This gene shares sequence similarity with mouse LLRep3. It is co-transcribed with the small nucleolar RNA gene U64, which is located in its third intron. As is typical for genes encoding ribosomal proteins, there are multiple processed pseudogenes of this gene dispersed through the genome. Interactions RPS2 has been shown to interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization advocating for the legal and human rights of chi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPSA (gene)
40S ribosomal protein SA is a ribosomal protein that in humans is encoded by the ''RPSA'' gene. It also acts as a cell surface receptor, in particular for laminin, and is involved in several pathogenic processes. This protein has been variously called Ribosomal protein SA; RPSA; LamR; LamR1; 37 kDa Laminin Receptor Precursor; 37LRP; 67 kDa Laminin Receptor; 67LR; 37/67 kDa Laminin Receptor; LRP/LR; LBP/p40; and p40 ribosome-associated protein. Ribosomal protein SA and RPSA are the approved name and symbol. Gene Multiple copies of the RPSA-like gene exist; however, most of them are pseudogenes thought to have arisen from retropositional events. Two alternatively spliced transcript variants encoding the same protein have been found for this gene. The complementary DNA (cDNA) of the RPSA gene is formed by the assembly of seven exons, six of which correspond to the coding sequence. Structure The amino acid sequence of RPSA, deduced from the sequence of its cDNA, includes 295 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 mRNAs has been shown to be translated by internal ribosome entry. IRES structure Nucleotides 1� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPS3 (gene)
40S ribosomal protein S3 is a protein that in humans is encoded by the ''RPS3'' gene. Function Ribosomes, the organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins. This gene encodes a ribosomal protein that is a component of the 40S subunit, where it forms part of the domain where translation is initiated. The protein belongs to the S3P family of ribosomal proteins. Studies of the mouse and rat proteins have demonstrated that the protein has an extraribosomal role as an endonuclease involved in the repair of UV-induced DNA damage. The protein appears to be located in both the cytoplasm and nucleus but not in the nucleolus The nucleolus (; : nucleoli ) is the largest structure in the cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of ribosome biogenesis. The nucleolus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPS3A (gene)
40S ribosomal protein S3a is a protein that in humans is encoded by the ''RPS3A'' gene. Ribosomes, the organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins. This gene encodes a ribosomal protein that is a component of the 40S subunit. The protein belongs to the S3AE family of ribosomal proteins. It is located in the cytoplasm. Disruption of the gene encoding rat ribosomal protein S3a, also named v-fos transformation effector protein, in v-fos-transformed rat cells results in reversion of the transformed phenotype. Transcript variants utilizing alternative transcription start sites have been described. This gene is co-transcribed with the U73A and U73B small nucleolar RNA genes, which are located in its fourth and third introns, respectively. As is typical for genes encoding ribosomal proteins, there are multiple processed pseu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RPS4X
40S ribosomal protein S4, X isoform is a protein that in humans is encoded by the ''RPS4X'' gene. Ribosomes, organelles that catalyze protein synthesis, consist of a small 40S subunit and a large 60S subunit. Together these subunits are composed of 4 RNA species and approximately 80 structurally distinct proteins. This gene encodes ribosomal protein S4, a component of the 40S subunit. Ribosomal protein S4 is the only ribosomal protein known to be encoded by more than one gene, namely this gene and ribosomal protein S4, Y-linked (RPS4Y). The 2 isoforms encoded by these genes are not identical, but are functionally equivalent. Ribosomal protein S4 belongs to the S4E family of ribosomal proteins. This gene is not subject to X-inactivation. It has been suggested that haploinsufficiency of the ribosomal protein S4 genes plays a role in Turner syndrome; however, this hypothesis is controversial. As is typical for genes encoding ribosomal proteins, there are multiple processed pseudogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
