In bacteria, the initiator tRNA carries and it is brought to the ribosome by
methionine: IF1
methionine: IF2
N-formylmethionine: IF1
N-formylmethionine, IF2
N-formylmethionine: IF3
The Correct Answer and Explanation is :
The correct answer is: N-formylmethionine, IF2
In bacteria, the initiator tRNA (tRNA^fMet) carries the amino acid N-formylmethionine (fMet). This modified methionine is the first amino acid incorporated into the growing polypeptide chain during protein synthesis. The formylation of methionine distinguishes the initiator tRNA from other methionine-carrying tRNAs that are used to incorporate methionine at positions other than the start codon within mRNA.
The initiation phase of protein synthesis in bacteria involves several key factors, among which IF2 is crucial. IF2 (Initiation Factor 2) is a GTPase necessary for the proper assembly of the ribosomal initiation complex. Its primary role is to escort the initiator tRNA charged with N-formylmethionine to the P site of the small ribosomal subunit. This is a critical step in the initiation process because it positions the initiator tRNA correctly at the start codon (AUG) of the mRNA, ensuring that protein synthesis starts at the correct point.
IF1 and IF3, the other initiation factors, also play essential roles, but they do not directly interact with the tRNA in the manner that IF2 does. IF1 helps to stabilize the binding of the small ribosomal subunit to mRNA and prevents premature association with the large subunit. IF3, on the other hand, assists in the disassembly of ribosomes after the termination of translation and helps prevent premature association of the small and large ribosomal subunits in preparation for initiation.
The specificity of IF2 for the initiator tRNA, combined with the unique structure of tRNA^fMet that carries N-formylmethionine, ensures the fidelity of the initiation process in bacterial protein synthesis. This specificity is critical for the accurate translation of genetic information from mRNA into functional proteins. Thus, the correct answer highlights the specialized roles of both the amino acid carrier (N-formylmethionine) and the molecular escort (IF2) that introduces the initiator tRNA into the ribosome to start protein synthesis.
Now, I’ll generate an image that visually represents this molecular interaction.
Here is an illustration representing the molecular interaction in bacterial protein synthesis, showing the initiator tRNA carrying N-formylmethionine guided to the ribosome by the initiation factor IF2. This visual can help in understanding how these components interact during the initiation phase of protein synthesis in bacteria.
