Role of tRNA in Translation

Introduction to Translation

Translation is the process in which the information carried by mRNA (messenger RNA) is used to synthesise a polypeptide chain, which ultimately forms a protein. This process takes place at the ribosome.

Involvement of tRNA in Translation

1. tRNA Definition

tRNA (transfer RNA) is a type of RNA molecule that plays a crucial role in translation. It carries specific amino acids to the ribosome during protein synthesis.

2. Translation Initiation

Translation begins at a start codon on the mRNA. The start codon (usually AUG) signals the ribosome to assemble and initiate translation.

3. Translation Termination

Translation ends at a stop codon on the mRNA. The stop codon (e.g., UAA, UAG, or UGA) signals the ribosome to terminate protein synthesis.

Anticodons and Codons

Anticodons

tRNA molecules have a region called the anticodon, which is a sequence of three nucleotides complementary to a specific codon on the mRNA. Anticodons play a crucial role in ensuring that the correct amino acid is added to the growing polypeptide chain.

Codons

Codons are sequences of three nucleotides on the mRNA that correspond to specific amino acids. Each codon codes for a specific amino acid. For example, AUG codes for methionine, and UAA is a stop codon.

---

Role of tRNA in Translation

Complementary Base Pairing in Translation

Complementary Base Pairing

• Complementary Base Pairing: The interaction between tRNA anticodons and mRNA codons relies on complementary base pairing. For example, if the mRNA codon is AUG, the complementary tRNA anticodon is UAC.
• Example: If the mRNA sequence contains the codon UAC, a tRNA molecule with the anticodon AUG will bind to it, carrying the amino acid methionine

Translation Process

1. Amino Acid Delivery

tRNA molecules deliver specific amino acids to the ribosome. Each tRNA molecule carries one type of amino acid and has an anticodon that matches a particular mRNA codon.

2. Formation of Peptide Bonds

As tRNA molecules bring their amino acids to the ribosome, the ribosome facilitates the formation of peptide bonds between adjacent amino acids. This process links the amino acids together, forming a growing polypeptide chain.

3. Ribosome Movement

The ribosome moves along the mRNA, reading the codons and ensuring that the corresponding tRNA molecules with the appropriate amino acids are brought in to continue protein synthesis.

4. Polypeptide Formation

This process continues until a stop codon is encountered on the mRNA. At that point, translation terminates, and the polypeptide chain is released.

tRNA Exit from the Ribosome

Polypeptide Release

As the polypeptide chain is formed, it exits the ribosome.

tRNA Departure

Once the tRNA molecules have delivered their amino acids and the polypeptide chain has been extended, they leave the ribosome to be reloaded with new amino acids for future rounds of translation.

---

Role of tRNA in Translation

Example of Translation

Let's consider an example of translation:

1. mRNA Sequence

Suppose the mRNA sequence reads AUG-UCG-CAA-UAA. This sequence contains a start codon (AUG), codons for serine (UCG) and glutamine (CAA), and a stop codon (UAA).

2. tRNA Involvement

tRNA molecules with the anticodons CAU (complementary to AUG), AGC (complementary to UCG), and GUU (complementary to CAA) bring in the corresponding amino acids, methionine, serine, and glutamine, respectively.

3. Ribosome Movement

The ribosome reads the mRNA sequence, and as each codon is exposed, the corresponding tRNA molecule with the appropriate amino acid binds to it. Peptide bonds form between the amino acids, creating a polypeptide chain.

4. Termination

Translation continues until the ribosome reaches the stop codon (UAA). At this point, translation terminates, and the polypeptide chain is released.

Summary

In summary, translation is the process in which tRNA molecules play a central role in synthesising a polypeptide chain from the information carried by mRNA. tRNA molecules carry specific amino acids to the ribosome, where they bind to complementary codons on the mRNA. Peptide bonds form between the amino acids, creating a growing polypeptide chain. Translation begins at a start codon and ends at a stop codon on the mRNA. Once translation is complete, tRNA molecules leave the ribosome, and the polypeptide chain is released. This process allows cells to produce the proteins necessary for various biological functions.