protein-and-peptides The elongation of peptide chain is a fundamental stage in protein synthesis, where the polypeptide chain grows by the sequential addition of amino acids. This crucial process occurs on the ribosome, guided by the messenger RNA (mRNA) sequence. Understanding the mechanism of peptide chain elongation is key to comprehending how genetic information is translated into functional proteins.
During the elongation phase, the ribosome moves along the mRNA molecule in a stepwise manner, reading codons (three-nucleotide sequences). For each codon, a specific aminoacyl-tRNA (a tRNA molecule carrying a particular amino acid) binds to the ribosome. This binding is facilitated by elongation factors, which are proteins that assist in the process作者：GJ Browne·2002·被引用次数：644—Theelongationphase of mRNA translation is the stage at which thepolypeptideis assembled and requires a substantial amount of metabolic energy..
The elongation cycle involves several key steps:
1. Aminoacyl-tRNA Binding: An aminoacyl-tRNA, matching the next codon on the mRNA, enters the A-site (aminoacyl site) of the ribosome. This step requires energy, typically from GTP hydrolysis, and is mediated by elongation factors (e.Overview of translation (article) | Khan Academyg.7.4 Translation, EF-Tu in bacteria, eEF1A in eukaryotes)7.4 Translation.
2. Peptide Bond Formation: A peptide bond is formed between the amino acid carried by the incoming aminoacyl-tRNA and the growing polypeptide chain attached to the tRNA in the P-site (peptidyl site)作者：A Skoultchi·1970·被引用次数：62—Peptide chain elongation: indications for the binding of an amino acid polymerization factor, guanosine 5'-triphosphate-aminoacyl transfer ribonucleic acid .... This reaction is catalyzed by the peptidyl transferase activity of the ribosome, specifically the ribosomal RNA (rRNA).
3.Peptide Chain Elongation Translocation: The ribosome moves one codon down the mRNA. This shifts the tRNA that was in the P-site to the E-site (exit site), where it is released, and the tRNA that was in the A-site, now carrying the extended polypeptide chain, moves to the P-site. This translocation step also requires elongation factors (e.Regulation of peptide-chain elongation in mammalian cellsg., EF-G in bacteria, eEF2 in eukaryotes) and GTP hydrolysisPolypeptide Chain Elongation in Protein Biosynthesis.
This cycle repeats, with each turn adding one amino acid to the growing polypeptide chain, leading to the stepwise elongation of the polypeptide.7.4 Translation
Several molecular components are essential for efficient peptide chain elongation:
* Ribosomes: These are the cellular machinery responsible for protein synthesis, composed of ribosomal RNA (rRNA) and ribosomal proteins.作者：CG Proud·1994·被引用次数：149—In most eukaryotes,two distinct protein elongation factors (eEF-1 and eEF-2) are required for elongation. Each is active as a complex with GTP. They provide the structural framework and catalytic activity for translation.
* mRNA: The messenger RNA molecule carries the genetic code from DNA to the ribosome, dictating the sequence of amino acids to be incorporated.
* tRNA: Transfer RNA molecules act as adaptors, each carrying a specific amino acid and possessing an anticodon that recognizes a complementary codon on the mRNAStages of transcription: initiation, elongation & termination (article).
* Aminoacyl-tRNA Synthetases: These enzymes are responsible for accurately attaching the correct amino acid to its corresponding tRNA molecule, a process known as tRNA charging.
* Elongation Factors: These are a class of proteins that play critical roles in promoting the binding of aminoacyl-tRNAs, peptide bond formation, and translocation of the ribosome along the mRNA. In eukaryotes, prominent elongation factors include eEF1 (involved in aminoacyl-tRNA binding) and eEF2 (involved in translocation).作者：ML Di Gioia·2005·被引用次数：50—In this work we describe a new, straightforward and general method for site-specific N-methylation of peptides during theelongation of peptide chainin ...
The elongation phase of translation is an energetically demanding process.作者：A Heyd·2003·被引用次数：28—The rate ofelongation of peptide chainsis a function of the concentration of the amino acid to be bound and the concentration of all other amino acids. In ... The formation of each peptide bond and the translocation steps require the hydrolysis of guanosine triphosphate (GTP), a high-energy molecule. This metabolic energy expenditure ensures the fidelity and efficiency of protein synthesis.
Regulation of peptide chain elongation is crucial for cellular function.Regulation of peptide‐chain elongation in mammalian cells Factors such as the availability of amino acids, charged tRNAs, and elongation factors can influence the rate of protein synthesisPeptide Chain Elongation: GTP Cleavage catalysed by .... Additionally, specific cellular signaling pathways can modulate the activity of elongation factors, allowing the cell to adjust protein production in response to its needs or environmental conditions.A mathematical model for elongation of a peptide chain For instance, certain factors, like eIF5A, have been shown to facilitate the elongation of specific stretches of amino acids, such as consecutive prolinesElongation factors are a class of proteins that aid in the translational elongationof a developing polypeptide from the first to the last peptide bond at the ....
While the fundamental mechanism of peptide chain elongation is conserved across all life forms, there are some differences between prokaryotes and eukaryotes.Polypeptide elongation Eukaryotes typically utilize distinct protein elongation factors, such as eEF-1 and eEF-2, which function in complexes with GTPPolypeptide Chain Elongation in Protein Biosynthesis. The regulation and specific protein factors involved can vary, reflecting the greater complexity of eukaryotic cellular processes.
In summary, the elongation of peptide chain is a dynamic and precisely controlled process that builds proteins based on the genetic instructions encoded in mRNA. It involves the coordinated action of ribosomes, tRNAs, mRNA, and various protein elongation factors, all powered by the hydrolysis of GTP, to ensure the accurate and efficient synthesis of functional polypeptides.Peptide-chain elongation in eukaryotes
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