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What are the 2 stages of protein synthesis

There are almost no significant differences in the protein synthesis steps in prokaryotes and eukaryotes, however there is one major distinction between the structure of the mRNAs — prokaryotes often have several coding regions polycistronic mRNAwhile the eukaryotic mRNA has only one coding region monocistronic mRNA.

The main protein synthesis steps are: Initiation Elongation Termination In most of the aspects, the process in eukaryotes follow the same simple protein synthesis steps as in prokaryotes.

However there are specific differences that could be outlined. For example, one important difference is that in prokaryotic cells the process of translation starts before transcription is completed. This coupling is defined because prokaryotes have no nuclear membrane and thus there is no physical separation of the two processes.

  • Each amino acid is coded for three letters word of nucleic acid;
  • Initiation of polypeptide chain;
  • After the formation of 70S-mRNAf-met-tRNAfmet complex, the elongation of polypeptide chain occurs by the regular addition of amino acids in the following steps:

Protein Synthesis Initiation The first of protein synthesis steps is initiation that cover the assembly of the translation system components and precedes the formation of peptide bonds. The components involved in the first step of protein synthesis are: Two mechanisms are involved in the recognition of nucleotide sequence AUG by the ribosome, which actually initiates translation: Shine-Dalgarno SD sequence - In Escherichia coli is observed sequence with high percentage of purine nucleotide bases, known as the Shine-Dalgarno sequence.

Thus the two complementary sequences can couple, which facilitates the positioning of the 30S ribosomal subunit on the mRNA in proximity to the initiation codon.

What Is The Second Step Of Protein Synthesis

The mechanism is slightly different in eukaryotes because they do not have SD sequences. However this process requires energy from ATP. The charged initiator transport RNA aproaches the P site on the small ribosomal subunit. In bacteria and in mitochondriaa methionine is attached to the initiator tRNA an subsequently a formyl group is added by the enzyme transformylase, which uses N10-formyl tetrahydrofolate as the carbon donor — finally a N-formylated methionine is attached to the initiator tRNA.

For comparison, in eukaryotes, the initiator transport RNA attaches a non formylated methionine. In the last step of the initiation, the large ribosomal subunit joins the complex formed by now, and thus a fully functional ribosome is formed. Translation Elongation Translation elongation is second in protein synthesis steps.

5 Major Stages of Protein Synthesis (explained with diagram) | Biology

During the elongation step the polypeptide chain adds amino acids to the carboxyl end the chain protein grows as the ribosome moves from the 5' -end to the 3'-end of the mRNA. The peptidyl-transferase is an important enzyme which catalyzes the formation of the peptide bonds.

  • One of these binding sites is responsible for binding of mRNA;
  • The process of translation begins when the mRNA molecule binds to the ribosome;
  • However there are specific differences that could be outlined;
  • The hydrolysis of GTP provides energy for the translocation;
  • Eukaryotic Ribosome The eukaryotic ribosomes slightly differ from these of the prokaryotes.

The enzymatic activity is found to be intrinsic to the 23S rRNA found in the large ribosomal subunit. Because this rRNA catalyzes the polypeptide bound formation reaction, it is named as a ribozyme.

Protein Synthesis Steps

The transport RNA at the P site carries the polypeptide synthesized by now, while on the A site is located a tRNA, which is bound to a single amino acid. After the peptide bond has been formed between the polypeptide and the amino acid, the newly formed polypeptide is linked to the tRNA at the A site.

  1. This reaction is brought about by the binding of an amino acid with ATP.
  2. The peptidyl-transferase is an important enzyme which catalyzes the formation of the peptide bonds.
  3. Since the dipeptidyl tRNA is still attached to second codon Fig.

Once this step is completed, the ribosome moves 3 nucleotides toward the 3'-end of the mRNA. This is an iterative process that is repeated until the ribosome reaches the termination codon. In prokaryotes, these codons are recognized by different release factors abbreviated with RF.

  1. Since the dipeptidyl tRNA is still attached to second codon Fig.
  2. Major steps involved in mechanism of Protein Synthesis are 1. A-site for attachment of tRNA.
  3. It can form an initiation complex with 30S subunit of another ribosome. Elongation of Polypeptide Chain.

When these release factors bind the complex, this cause in hydrolysis of the bond linking the peptide to the tRNA at the P site and releases the nascent protein from the ribosome. In contrast, the eukaryote cells have just one release factor, eRF, which can recognize all three termination codons.

  • DNA molecules provide the information for their own replication;
  • During the elongation step the polypeptide chain adds amino acids to the carboxyl end the chain protein grows as the ribosome moves from the 5' -end to the 3'-end of the mRNA;
  • In order to be able to code for one of the 20 different amino acid residues building polypeptides, the information within the nucleotide sequences must be encoded by a sequence of at least 3 nucleotides, called a triple or codon;
  • For comparison, in eukaryotes, the initiator transport RNA attaches a non formylated methionine.

A second factor is involved - eRF-3, with a similar function to the RF-3 in prokaryote cells. The protein synthesis steps in prokaryotes are summarized in figure below.

2 Major Steps Involved in Mechanism of Protein Synthesis : Transcription and Translation

Some antibiotic inhibitors that could be involved at different protein synthesis steps are: