Question

What are the enzymes used in translation?

Answer 1

Hint: The ribosome, a specialised organelle found in all cells, houses the translation machinery. Mature mRNA molecules in eukaryotes must exit the nucleus and migrate to the cytoplasm, where ribosomes are found. The process of transcription and translation use the information contained in DNA to make proteins.

Complete answer:

A ribosome is a complex macromolecule composed of catalytic rRNAs (called ribozymes) and structural rRNAs, as well as many distinct polypeptides. Ribosomes dissociate into large and small subunits when they are not synthesizing proteins and reassociate during the initiation of translation. The small subunit is responsible for binding the mRNA template, whereas the large subunit binds tRNAs. Transfer RNA (t-RNA) is a type of RNA molecule that can bind to three base pair codons on messenger RNA (mRNA) and carry the amino acid encoded by the codon. Therefore, tRNAs actually “translate” the language of RNA into the language of proteins. These molecules interact with three factors: aminoacyl tRNA synthetases, ribosomes, and mRNA. Each mRNA molecule is simultaneously translated by many ribosomes, all synthesizing protein in the same direction: reading the mRNA from 5′ to 3′ and synthesizing the polypeptide from the N terminus to the C terminus. 

The enzymes that are used in translation are as follows-

i) Aminoacyl-tRNA synthetases catalyse the binding of a given amino acid to the 3' end of its cognate tRNA, which is a crucial step in protein biosynthesis. They do so by creating an energy-dense Aminoacyl-adenylate intermediate of the cognate amino acid, which then transfers the amino acid to the tRNA. Aminoacyl-tRNA synthetase hydrolysis ATP to add an amino acid to the 3'-end of tRNA's CCA sequence. Charging is the term for this operation, and the tRNA is called charged.

The initiator tRNA interacts with the start codon AUG of the mRNA and carries a formylated methionine (fMet) to insert it at the beginning (N terminus) of every polypeptide chain.

ii) Peptidyl transferase is an enzyme found in the larger of the two ribosomal subunits that catalyses the transfer of formyl methionine from the tRNA to which it is attached to the second amino acid. The formation of each peptide bond is catalyzed by peptidyl transferase.

iii) Some species use the initiator tRNAMet (also known as tRNAfmet) for translation initiation.

Note: During protein synthesis, translation is the method of converting the sequence of a messenger RNA molecule into a sequence of amino acids which is called the protein. The termination of translation occurs when a nonsense codon (UAA, UAG, or UGA) is encountered for which there is no complementary tRNA. The small and large ribosomal subunits dissociate from the mRNA.