Question

Describe the processing events that occur during the production of tRNA in E. coli.

Short answer

Transfer RNA (tRNA) production in E. coli involves transcription of the tRNA gene into a precursor tRNA molecule, processing and modification of the precursor tRNA, and maturation of the tRNA into its final form that is ready for participation in protein synthesis.

Step-by-step solution

Initiation of Transcription

DNA sequence for the tRNA gene in the genome of E. coli is transcribed into a precursor tRNA, or pre-tRNA. This transcription process is initiated by the RNA polymerase binding to a specific sequence on the DNA known as the promoter.

Elongation

After the initiation, the RNA polymerase proceeds with the process of elongation where it synthesizes the pre-tRNA molecule, using the DNA strand as a template.

Termination

The transcription continues until the RNA polymerase reaches a termination sequence on the DNA. At this point, the RNA polymerase detaches from the DNA, signalling the end of transcription.

Pre-tRNA Processing

The pre-tRNA produced is then processed to form a functional tRNA molecule. This involves removal of extra nucleotides at both ends of the pre-tRNA molecule and addition of a 'CCA' sequence at the 3' end. This is done by various enzymes, such as RNase P and RNase D.

Base Modifications

Some of the nucleotides are then chemically modified at specific positions.

Formation of tRNA Structure

The processed tRNA then folds into a clover-leaf structure, which is the characteristic structure of tRNA.

Final Maturation

The tRNA is now fully mature and ready for participation in the process of translation, during which the tRNA helps to add the correct amino acids to the growing peptide chain in response to the codons in the mRNA script.