Anticodon- Definition, Principle, Functions, Examples

Anticodon- Definition, Principle, Functions, Examples

An Anticodon is a triplet of nucleotides in a transfer RNA (tRNA) molecule complementary to a particular codon on a messenger RNA (mRNA) strand. It plays an important role in protein formation. The mechanism behind its function is complementary base pairing, in tRNA couples with the codon on mRNA, guaranteeing that the right amino acid is absorbed into the developing polypeptide chain. Each tRNA is connected to a certain amino acid, and it guarantees that the mRNA sequence is correctly delivered.

Definition of Anticodon

They are nucleotide sequences that are complementary to codons. They are contained in tRNAs and allow them to align the right amino acid with an mRNA during protein synthesis. During protein formation, amino acids form a string, similar to pearls on a necklace. Because amino acids have diverse characteristics, it is critical to employ the correct ones in the appropriate areas. Placing the incorrect one in a position might render a protein useless or even hazardous to the cell. This image depicts a developing protein chain. To the bottom left, you can see tRNAs transporting amino acids entering the ribosomal complex.

Principle Of Anticodon

  • The arrangement of mRNA and tRNA is antiparallel.
  • The first base of the codon on mRNA (5to 3) binds with the third base of it on the tRNA to initiate the process of translation.
  • Each tRNA carries a specific amino acid and it binds to the mRNA complementary codon on the 30s subunit in prokaryotes and the 40s subunit in eukaryotes.
  • During this process, the first one is accepted by the A site, and then it binds to the P site on mRNA where the growing polypeptide of the protein is held together.
  • Once the amino acid carried by the tRNA is transferred it moves 3 nucleotides further to the E site (Exit).
  • If it is considered that perfect paring occurs between codon and anticodon, then unique tRNA will be required for every amino acid.
  • However, this is not the case. Some tRNAs include a nucleotide Inosinate (I) which contains an uncommon base known as ‘hypoxanthine’.

How Anticodons Work

tRNA Charging

An enzyme known as aminoacyl-tRNA synthetase binds each tRNA molecule to a particular amino acid. Aminoacylation, or tRNA charging, is the term for this process. The enzyme makes ensuring that the right tRNA, which contains the matching anticodon, is connected to the right amino acid.

mRNA Binding

The ribosome attaches itself to an mRNA molecule during translation to start reading the codon sequence, which consists of three nucleotide sequences.

Transfer and Discharge

The tRNA is moved from the P site to the E site (exit site), where it is released, by the ribosome as it travels along the mRNA to the subsequent codon. The process continues until a stop codon is reached, indicating the conclusion of translation, at which point the next charged tRNA with the proper entrance in the A site.

Function and example

Methionine

  • Codon on mRNA: AUG
  • Anticodon on tRNA: UAC
  • Function: The tRNA with the UAC delivers methionine, the amino acid coded by AUG. Methionine often serves as the start codon, initiating protein synthesis.

Phenylalanine

  • Codon on mRNA: UUU or UUC
  • Anticodon on tRNA: AAA or AAG
  • Function: The tRNA with AAA or AAG pairs with UUU or UUC, delivering phenylalanine.

Serine

  • Codon on mRNA: UCU, UCC, UCA, or UCG
  • Anticodon on tRNA: AGA, AGG, AGU, or AGC
  • Function: Different tRNAs with these pair with the various codons for serine, delivering the amino acid serine.

Valine

  • Codon on mRNA: GUU, GUC, GUA, or GUG
  • Anticodon on tRNA: CAA, CAG, CAU, or CAC
  • Function: The tRNAs with these deliver valine.

Frequently Asked Questions

What is an anticodon?

It is a sequence of three nucleotides in a transfer RNA (tRNA) molecule complementary to a specific codon in messenger RNA (mRNA). It plays a crucial role in translating the genetic code into proteins.

How do anticodons function in protein synthesis?

They function by pairing with complementary codons on the mRNA strand during translation. This pairing ensures that the correct amino acids are added to the growing polypeptide chain, maintaining the accuracy of protein synthesis.

What is the principle of codon pairing?

The principle is based on complementary base pairing, where adenine (A) pairs with uracil (U), and guanine (G) pairs with cytosine (C).

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