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Initiation of translation in bacteria involves the assembly of the components of the translation system, which are: the two ribosomal subunits (50S and 30S subunits); the mature mRNA to be translated; the tRNA charged with N-formylmethionine (the first amino acid in the nascent peptide); guanosine triphosphate (GTP) as a source of energy, and the three prokaryotic initiation factors IF1, IF2 ...
A bacterial initiation factor (IF) is a protein that stabilizes the initiation complex for polypeptide translation. Translation initiation is essential to protein synthesis and regulates mRNA translation fidelity and efficiency in bacteria. [1] The 30S ribosomal subunit, initiator tRNA, and mRNA form an initiation complex for elongation. [2]
Thus translation and transcription are parallel processes. Bacterial mRNA are usually polycistronic and contain multiple ribosome binding sites. Translation initiation is the most highly regulated step of protein synthesis in prokaryotes. [5] The rate of translation depends on two factors: the rate at which a ribosome is recruited to the RBS
The prokaryotic initiation factor, IF3, assists with start site specificity, as well as mRNA binding. [2] [3] This is in comparison with the eukaryotic initiation factor, eIF1, who also performs these functions. The elF1 structure is similar to the C-terminal domain of IF3, as they each contain a five-stranded beta sheet against two alpha helices.
In bacteria, the initiation of translation occurs when IF-3, along with the 30S ribosomal subunit, bind to the Shine–Dalgarno (SD) sequence of the 5′ UTR. [5] This then recruits many other proteins, such as the 50S ribosomal subunit, which allows for translation to begin. Each of these steps regulates the initiation of translation.
In prokaryotes (bacteria and archaea), translation occurs in the cytosol, where the large and small subunits of the ribosome bind to the mRNA. In eukaryotes, translation occurs in the cytoplasm or across the membrane of the endoplasmic reticulum through a process called co-translational translocation.
The σ-factor dissociates from the core enzyme and elongation proceeds. This signals the end of the initiation phase and the holoenzyme is now in core polymerase form. [4] Abortive cycling occurs prior to sigma factor release. The promoter region is a prime regulator of transcription. Promoter regions regulate transcription of all genes within ...
Initiation of translation is regulated by the accessibility of ribosomes to the Shine-Dalgarno sequence.This stretch of four to nine purine residues are located upstream the initiation codon and hybridize to a pyrimidine-rich sequence near the 3' end of the 16S RNA within the 30S bacterial ribosomal subunit. [1]