Question

Initiation of polypeptide chain in eukaryotic protein synthesis is induced by which amino acid?
A) Methionine
B) Leucine
C) Lysine
D) Glycine

Answer 1

Hint:In eukaryotic cells, initiation of the protein synthesis always starts with the codon AUG also known as start codon. In the case of prokaryotes, the start sequence of the protein translation is a purine rich sequence of 5' which helps in the identification of start codon.

Complete answer:
The process of protein synthesis in the prokaryotes, eukaryotes and archaea is almost similar but it differs a little bit in each of the following organisms because of the presence of mechanisms and available proteins formed during their evolution.

RNA which is responsible for the protein production is rRNA, tRNA and mRNA. After transcription of the DNA protein synthesis or translation starts.

Smaller subunit of the ribosome which is floating in the cytoplasm gets attached to the 5’ end of the mRNA and starts scanning for the start codon in the sequence. During the scanning process, helicases and other required enzymes come to the translational complex and initiation factors also come and bind to start the process.

Now, elongation of the protein peptide starts with the elongation factors like EF1-alpha tRNA brings the amino acid complementary to the mRNA sequence and rRNA helps in the catalysis of the reaction. The chain starts growing and elongating with the adding of the amino acids according to the mRNA sequence.
Termination of the process takes place with the help of one factor eRF1. And IF3 factors prevent the reassociation of the translational complex.

Thus, we can say that start codon is the methionine for the eukaryotic translation. And option ‘A’ is the correct answer.

Note:Protein formation takes place in the ribosomes of the cells and eukaryotic ribosomes are large in the size s compared to prokaryotic ribosomes. Eukaryotic cells have larger subunits of 60S and smaller subunits of 40S. In prokaryotes, larger subunit is of 50S and smaller subunit of 30S.