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A ribosome is made up of two subunits, a small subunit, and a large subunit. These subunits come together before the translation of mRNA into a protein to provide a location for translation to be carried out and a polypeptide to be produced. [3] The choice of amino acid type to add is determined by a messenger RNA (mRNA) molecule. Each amino ...
Translation is one of the key energy consumers in cells, hence it is strictly regulated. Numerous mechanisms have evolved that control and regulate translation in eukaryotes as well as prokaryotes. Regulation of translation can impact the global rate of protein synthesis which is closely coupled to the metabolic and proliferative state of a cell.
Structure of rabbit eIF3 in the context of the 43S PIC, showing subunits a, c, e, f, h, k, l, and m. [1]Eukaryotic initiation factor 3 (eIF3) is a multiprotein complex that functions during the initiation phase of eukaryotic translation. [2]
Initiation of translation is regulated by the accessibility of ribosomes to the Shine-Dalgarno sequence. This stretch of four to nine purine residues are located upstream the initiation codon and hybridize to a pyrimidine-rich sequence near the 3' end of the 16S RNA within the 30S bacterial ribosomal subunit . [ 1 ]
Poly(A)-binding protein is exported to the cytoplasm with the RNA. mRNAs that are not exported are degraded by the exosome. [39] [40] Poly(A)-binding protein also can bind to, and thus recruit, several proteins that affect translation, [39] one of these is initiation factor-4G, which in turn recruits the 40S ribosomal subunit. [41]
The eIF2 alpha subunit is characterized by an OB-fold domain and two beta strands. This subunit helps to regulate translation, as it becomes phosphorylated to inhibit protein synthesis. [2] The eIF4F complex supports the cap-dependent translation initiation process and is composed of the initiation factors eIF4A, eIF4E, and eIF4G.
[3] For example, a DNA sequence for a protein of interest could be cloned or subcloned into a high copy-number plasmid containing the lac (often LacUV5) promoter, which is then transformed into the bacterium E. coli. Addition of IPTG (a lactose analog) activates the lac promoter and causes the bacteria to express the protein of interest. [2]
Initiation of translation in bacteria involves the assembly of the components of the translation system, which are: the two ribosomal subunits (50S and 30S subunits); the mature mRNA to be translated; the tRNA charged with N-formylmethionine (the first amino acid in the nascent peptide); guanosine triphosphate (GTP) as a source of energy, and the three prokaryotic initiation factors IF1, IF2 ...