Describe initiation step of translation in prokaryotes.

Explanation

After initiation step of translation, the next steps are as follows
(i) Elongation It involves the addition of further amino acids to the polypeptide chain. For elongation, initiation complex, different aminoacyl tRNAs, two elongation factors (Et-Tu and EF-Ts) and GTP (energy source) are required. Elongation involves three steps, that are
(a) Binding of incoming aminoacyl rRNA The incoming aminoacyl-tRNA binds to a complex of EF-Tu-GTP to result in a aminpacyl tRNA-Tu-GTP complex. This complex binds to the A site of 70S initiation complex.
Then, GTP is hydrolysed to GDP and Pi and EF-Tu-GDP complex is released from the ribosome
(b) Peptide bond formation A peptide bond (Co-NH) forms between the carboxyl group of methionine and amino group of the second amino acid. The reaction is catalysed by peptidyl transferase enzyme.
(c) Translocation The peptidyl tRNA bound to A-site comes to P-site of the ribosome, the empty tRNA at P-site comes to the E-site and A-site gets occupied by new codon. The ribosome moves from codon to codon along the mRNA in 5 `rarr` 3 direction. Amino acids are added one by one, translated into polypeptide sequence dictated by DNA and represented by mRNA.
(iii) Termination Termination of the synthesis of polypeptide is brought about by the presence of any one of the three termination codons on the mRNA. These termination codons are recognised by any one of the three release factors. RF1, RF2 and RF3. When a release factor, binds to the stop codon, the polypeptide synthesis is terminated. As a result, the complete polypeptide is released from the ribosome.