Question

Explain aminoacylation of tRNA.

Answer 1

Hint: A type of RNA molecule that helps to decode a sequence of messenger RNA ( mRNA) into a protein is ribonucleic acid transfer (tRNA). During translation, tRNAs function at particular sites in the ribosome, a process that synthesises the protein of the mRNA molecule.

Complete Answer:
Aminoacyl-tRNA (also aa-tRNA or charged tRNA) is a tRNA that is chemically bonded (charged) to its cognate amino acid.
The aa-tRNA delivers the amino acid to the ribosome for integration into the polypeptide chain that is formed during translation, along with specific elongation factors.
An amino acid alone is not the substrate required to allow peptide bonds within a growing polypeptide chain to form.
 Instead, to form their respective aa-tRNA, amino acids must be' charged' or aminoacylated with a tRNA. Each amino acid has its own specific aminoacyl-tRNA synthetase used to bind chemically to the tRNA to which it is specific or, in other words, to which it is "cognate."
It is important to pair a tRNA with its cognate amino acid, as it ensures that only the same amino acid that matches the tRNA anticodon and, in turn, matches the mRNA codon is used during protein synthesis.
Evolution has provided for the proofreading functionalities of aa-tRNA synthetases in order to prevent translational errors in which the incorrect amino acid is inserted into the polypeptide chain;
These processes ensure an amino acid is correctly matched with its cognate tRNA. Via the deacylation processes, amino acids that are misacylated with the proper tRNA substrate undergo hydrolysis.
There are two steps in the development of aminoacyl-tRNA. Next, the amino acid adenylation that forms the amino acid-AMP:
Amino Acid + ATP Acid-AMP + PPi
\[ \Rightarrow aa+ATP\overset{ARS}{\to}aa-AMP+PPi\]

Second, the residue of the amino acid is passed to the tRNA:
Aminoacyl-AMP + tRNA for Aminoacyl-tRNA + AMP
\[ \Rightarrow aa-AMP+tRNAaa\xrightarrow{ARS}aa-tRNAaa+AMP\]

The overall net reaction is as follows:
Amino Acid + ATP + tRNA $\to$ Amino Acid + AMP + PPi
\[ \Rightarrow aa+ATP+tRNA \to aa-tRNA+AMP+PPi\]

The net reaction is energetically favourable only because the pyrophosphate (PPi) is then hydrolyzed. Hydrolysis of pyrophosphate to two molecules of inorganic phosphate (Pi) reaction is highly energetic and causes two other reactions. Together, these highly exergonic reactions take place within the amino acid-tRNA synthetase specific to the amino acid.

Note: Certain antibiotics, such as tetracyclines, avoid the binding of aminoacyl-tRNA to the ribosomal subunit in prokaryotes. It is known that tetracyclines inhibit the attachment of aa-tRNA to the acceptor (A) site of prokaryotic ribosomes during translation. Tetracyclines are known to be a broad-spectrum antibiotic agent; these drugs have the ability to inhibit the growth of both gram-positive and gramme-negative bacteria, as well as other atypical microorganisms.