Language
Country/Area
No result found
How do stop codons control translation? Discover the mysterious power of RF1 and RF2!
In the translation process of the genetic code, the stop codon plays a vital role. These "stop signals" ensure the correct end of protein synthesis, and this process mainly relies on the intervention of release factors (RFs). During cellular translation, how these factors control the termination of translation, especially the two proteins RF1 and RF2, undoubtedly attracts attention.
Proteins known as release factors recognize stop codons in the mRNA sequence and promote the release of newly synthesized polypeptides from ribosomes.
Background of release factors
During the translation process, most codons are recognized by "charged" tRNA molecules. These molecules, called amino acid-tRNAs, carry the specific amino acid corresponding to the anticodon of each tRNA. According to the standard genetic code, there are three mRNA stop codes: UAG ("amber"), UAA ("chuochuo"), and UGA (another name for "cat's eye" or "beer"). These stops are not decoded by tRNA but are recognized by release factors.
In 1967, scientist Mario Capecchi discovered that the release factor was not a tRNA molecule but a protein. Further research found that different release factors recognize different termination codes.
Classification of release factors
Release factors can be divided into two categories. Class 1 release factors are responsible for recognizing the stop codon and binding to the A site of the ribosome in a tRNA-like manner, releasing the newly formed polypeptide while disassembling the ribosome. Class 2 release factors are GTPases, which enhance the activity of Class 1 release factors and help them dissociate from ribosomes.
Release factors in bacteria include RF1, RF2 and RF3 (or PrfA, PrfB, PrfC), among which RF1 recognizes UAA and UAG, while RF2 recognizes UAA and UGA.
Structure and function of release factors
Through crystallographic studies, scientists revealed the interaction mode of release factors and bacterial 70S ribosomes, demonstrating the detailed mechanism of RF1 and RF2 in stop code recognition. In addition, the cryo-electron microscopy structure of the mouse 80S ribosome and eRF1 and eRF3 was also obtained, showing the structural rearrangement caused by factors and further providing insight into this process.
When RF1 or RF2 binds to the A site of the ribosome, the release factor is activated and causes structural changes, ultimately leading to the release of the polypeptide.
The role of bacterial release factors
In bacteria, the first type of release factors can be divided into four domains, among which the important domains related to catalysis include the "amino acid anticodon" motif and the GGQ motif. These motifs play a key role in the process responsible for the hydrolysis of peptide-tRNA ester bonds. RF3 is also essential in this process because it is involved in the release of RF1/2 so that ribosomes can be used.
Function of eukaryotic and archaeal release factors
The eukaryotic release factor structure is also divided into four domains, and its N-terminal domain is specifically responsible for the recognition of the termination code. After binding to GTP, the release factor will move with the hydrolysis of GTP, which allows GGQ to enter the acyl transfer center of the ribosome for hydrolysis and completion of translation termination.
It is worth noting that in this process, the archaeal release factor system also demonstrated a similar mechanism to the eukaryotic system, further emphasizing the irreplaceable role these factors play in life processes.
At present, the scientific community is still full of enthusiasm for exploring the functions and structures of release factors. They undoubtedly play a key role in the translation process, but in future research, will new release factors or mechanisms of action be discovered? Woolen cloth?
