Protein synthesis:
See AlsoRibosomes, Transcription, TranslationUncovering the Relationship Between Genes and Proteins - ATA Scientific- Protein synthesis(translation) is the production of a polymer of a chain of amino acids which produces a functioning protein.
- It involves reading the information from mRNA (messenger RNA) to put together a chain of amino acids.
- Ribosomes are the structures that synthesize the protein chain.
- Protein synthesis requires a tRNA (transfer RNA) which helps in the transfer of an amino acid molecule to the growing chain.
- tRNA has anti-codons for the codons present on the mRNA molecule which helps to recognize the place of single amino acid.
- There are a total of 20 major common amino acids used in protein synthesis.
- There are five major steps of protein synthesis.
Major steps of protein synthesis:
A. Activation of amino acids:
- The activation of amino acids deals with the charging of tRNA and requires the enzyme aminoacyl RNA synthetase.
- It helps in the formation of the aminoacyl – AMP – enzyme complex.
- It yields the required energy from adenosine triphosphate (ATP).
B. Transfer of amino acids to tRNA:
- In this step, the aminoacyl – AMP – enzyme complex gets completely charged by reacting with the specific tRNA.
- The amino acid is transferred to the specific amino acid.
- Due to the transfer process, the enzyme aminoacyl tRNA synthetase, and the AMP molecule leave activating the tRNA.
- Hence the enzyme aminoacyl tRNA synthetase plays a major in the catalysis of covalently linking an amino acid to its cognate tRNA.
C. Initiation of polypeptide chain:
- The charged activated tRNA moves towards the larger subunit of the ribosome which already is attached to the mRNA strand.
- The mRNA strand is bound to the SOS sub-unit of ribosomes of 70S type.
- The ribosome reads the codon on the mRNA and the tRNA has the anticodon complementary to the specific codon on the mRNA.
- After specific recognition, the charged tRNA molecule enters the A-site (aminoacyl site) of the ribosome.
- The initiation codon of every polypeptide chain in prokaryotes is always for the amino acid methionine which is coded by the codon AUG or GUG (for valine).
- Further, the entry of successive new charged tRNA with another amino acid pushes the previously charged tRNA at the A-site to move into the P-site (peptidyl site).
- There is peptide formation between both amino acids at the P-site and A-site.
- The amino acid at the P-site gets removed from the tRNA and begins the formation of the peptide chain.
- The tRNA at the P-site enters into the E-site (exit) of the ribosome to leave the ribosome molecule and create space for the entry of a new charged tRNA molecule at the A-site.
- The cyclic process is repeated till the peptide chain grows and the mRNA is read until it reaches the termination codon.
D. Chain Termination:
- Once the ribosome reaches one of the three termination codons, UAG (Amber), UAA (Ochre), and UGA (Opal), it falls off from the mRNA.
- These codons are known as stop codons.
- They signal the termination of the growing peptide chain and hence, stop translation.
E. Protein translocation:
- There are different classes of ribosomes that assist in translation.
- The free poly-ribosomes directly release the growing peptide chain into the cytoplasm after the complete protein has been synthesized upon the termination.
- Whereas the membrane-bound polyribosomes do not release the protein chain directly into the cytoplasm, instead they divert the growing polypeptide chain into the lumen of ER for further post-translational modifications.
Protein synthesis:
See Also
Ribosomes, Transcription, TranslationUncovering the Relationship Between Genes and Proteins - ATA Scientific- Protein synthesis(translation) is the production of a polymer of a chain of amino acids which produces a functioning protein.
- It involves reading the information from mRNA (messenger RNA) to put together a chain of amino acids.
- Ribosomes are the structures that synthesize the protein chain.
- Protein synthesis requires a tRNA (transfer RNA) which helps in the transfer of an amino acid molecule to the growing chain.
- tRNA has anti-codons for the codons present on the mRNA molecule which helps to recognize the place of single amino acid.
- There are a total of 20 major common amino acids used in protein synthesis.
- There are five major steps of protein synthesis.
Major steps of protein synthesis:
A. Activation of amino acids:
- The activation of amino acids deals with the charging of tRNA and requires the enzyme aminoacyl RNA synthetase.
- It helps in the formation of the aminoacyl – AMP – enzyme complex.
- It yields the required energy from adenosine triphosphate (ATP).
B. Transfer of amino acids to tRNA:
- In this step, the aminoacyl – AMP – enzyme complex gets completely charged by reacting with the specific tRNA.
- The amino acid is transferred to the specific amino acid.
- Due to the transfer process, the enzyme aminoacyl tRNA synthetase, and the AMP molecule leave activating the tRNA.
- Hence the enzyme aminoacyl tRNA synthetase plays a major in the catalysis of covalently linking an amino acid to its cognate tRNA.
C. Initiation of polypeptide chain:
- The charged activated tRNA moves towards the larger subunit of the ribosome which already is attached to the mRNA strand.
- The mRNA strand is bound to the SOS sub-unit of ribosomes of 70S type.
- The ribosome reads the codon on the mRNA and the tRNA has the anticodon complementary to the specific codon on the mRNA.
- After specific recognition, the charged tRNA molecule enters the A-site (aminoacyl site) of the ribosome.
- The initiation codon of every polypeptide chain in prokaryotes is always for the amino acid methionine which is coded by the codon AUG or GUG (for valine).
- Further, the entry of successive new charged tRNA with another amino acid pushes the previously charged tRNA at the A-site to move into the P-site (peptidyl site).
- There is peptide formation between both amino acids at the P-site and A-site.
- The amino acid at the P-site gets removed from the tRNA and begins the formation of the peptide chain.
- The tRNA at the P-site enters into the E-site (exit) of the ribosome to leave the ribosome molecule and create space for the entry of a new charged tRNA molecule at the A-site.
- The cyclic process is repeated till the peptide chain grows and the mRNA is read until it reaches the termination codon.
D. Chain Termination:
- Once the ribosome reaches one of the three termination codons, UAG (Amber), UAA (Ochre), and UGA (Opal), it falls off from the mRNA.
- These codons are known as stop codons.
- They signal the termination of the growing peptide chain and hence, stop translation.
E. Protein translocation:
- There are different classes of ribosomes that assist in translation.
- The free poly-ribosomes directly release the growing peptide chain into the cytoplasm after the complete protein has been synthesized upon the termination.
- Whereas the membrane-bound polyribosomes do not release the protein chain directly into the cytoplasm, instead they divert the growing polypeptide chain into the lumen of ER for further post-translational modifications.
