Question

The effect of the antibiotic is to inhibit protein synthesis, and bacteria treated with it accumulate dipeptidyl-tRNA species What specific factor is the most likely target of the antibiotic? Support your argument with a brief description of the affected process.

Answer 1

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The protein synthesis involves the translation of nucleotide sequence of mRNA into the language of Amino acid sequence.

The protein synthesis proper can be divided into 3 stages

Initiation of translation

Elongation of translation

Termination of translation

The process of elongation can be again divided into 3 steps

Binding of aminoacyl tRNA to A site

The 80s initiation complex contains met-tRNA in the P site and the A site is free. Another amino acyl tRNA is placed in the A site. As the aminoacyl tRNA is placed in the A site, EF 1 alpha and GDP are recycled to bring another aminoacyl tRNA.

Peptide bond formation

The enzyme peptidyl transferase catalyses the formation of peptide bond. The net result of peptide Bond formation is the attachment of the growing peptide chain to the tRNA in the A site.

This whole complex is known as dipeptidyl tRNA.

Translocation

As the peptide bond formation occurs, the ribosome moves to the next codon of the mRNA. This process involves the movement of growing peptide chain from A site to P site. This requires EF2 & GTP. The given antibiotic blocks this step of transcription. The most likely target of the antibiotic is EF2.

The inhibition of this step will lead to accumulation of previous complex which dipeptidyl tRNA. It is provided in the question that there is accumulation of dipeptidyl tRNA species this prove this argument.