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Aminoacyl-tRNA (also aa-tRNA or charged tRNA) is tRNA to which its cognate amino acid is chemically bonded (charged). The aa-tRNA, along with particular elongation factors , deliver the amino acid to the ribosome for incorporation into the polypeptide chain that is being produced during translation.
Amino acid activation (also known as aminoacylation or tRNA charging) refers to the attachment of an amino acid to its respective transfer RNA (tRNA). The reaction occurs in the cell cytosol and consists of two steps: first, the enzyme aminoacyl tRNA synthetase catalyzes the binding of adenosine triphosphate (ATP) to a corresponding amino acid, forming a reactive aminoacyl adenylate ...
mediates the entry of the aminoacyl tRNA into a free site of the ribosome. [4] EF-Ts: eEF-1B (β γ) [2] serves as the guanine nucleotide exchange factor for EF-Tu, catalyzing the release of GDP from EF-Tu. [2] EF-G: eEF-2: catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation.
Once translation initiation is complete, the first aminoacyl tRNA is located in the P/P site, ready for the elongation cycle described below. During translation elongation, tRNA first binds to the ribosome as part of a complex with elongation factor Tu or its eukaryotic or archaeal counterpart. This initial tRNA binding site is called the A/T site.
The amino acid is joined by its carboxyl group to the 3' OH of the tRNA by an ester bond. When the tRNA has an amino acid linked to it, the tRNA is termed "charged". In bacteria, this aminoacyl-tRNA is carried to the ribosome by EF-Tu, where mRNA codons are matched through complementary base pairing to specific tRNA anticodons. Aminoacyl-tRNA ...
The ribosomal P-site plays a vital role in all phases of translation. Initiation involves recognition of the start codon (AUG) by initiator tRNA in the P-site, elongation involves passage of many elongator tRNAs through the P site, termination involves hydrolysis of the mature polypeptide from tRNA bound to the P-site, and ribosome recycling involves release of deacylated tRNA.
Elongation depends on eukaryotic elongation factors. At the end of the initiation step, the mRNA is positioned so that the next codon can be translated during the elongation stage of protein synthesis. The initiator tRNA occupies the P site in the ribosome, and the A site is ready to receive an aminoacyl-tRNA. During chain elongation, each ...
EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome. It is a G-protein , and facilitates the selection and binding of an aa-tRNA to the A-site of the ribosome.