Initiation:
(i) In prokaryotes, initiation requires the large and small ribosome subunits, the mRNA, initiation tRNA and three initiation factors (IFs).
(ii) Amino acids become activated by binding with its aminoacyl-tRNA synthetase in the presence of ATP
(iii) The AA-AMP-Enzyme complex formed react with specific tRNA to form amino acyl-tRNA complex.
AA-AMP-Enzyme complex + tRNA -----> AA-tRNA + AMP + Enzyme
(iv) The cap region of mRNA bind to the smaller subunit of ribosome.
(v) The ribosome have two sites— A-site and P-site.
(vi) The smaller subunit first binds the initiator tRNA and then attain to larger subunit so that initiation codon (AUG) come on the P-site.
(vii) The initiation tRNA, i.e., methionyl tRNA binds to the P-site.
Termination of polypeptide
(i) When the A-site of ribosome reach a termination codon which does not code for any amino acid as a result, no charged tRNA bind to A-site.
(ii) Dissociation of polypeptide from ribosome takes place which is catalysed by a ‘release factor’.
(iii) There are three termination codons namely UGA, UAG and UAA.
