stoppcapprótein

Stop-codon readthrough, also known as stop codon readthrough or ribosomal frameshifting, is a biological process in which the translation machinery of a cell (the ribosome) continues to synthesize a polypeptide chain beyond a normal stop codon. Normally, a stop codon (UAA, UAG, or UGA) signals the termination of protein synthesis. However, under certain conditions, the ribosome can misinterpret these codons, incorporating an amino acid and extending the polypeptide chain. This can lead to the production of a longer protein variant, often with altered or additional functions.

Several factors can promote stop-codon readthrough. These include specific sequences in the messenger RNA (mRNA) adjacent to the stop codon, the presence of certain transfer RNAs (tRNAs) that can partially bind to the stop codon, and the availability of aminoacyl-tRNAs. Ribosomal proteins and accessory factors can also influence the efficiency of readthrough.

Stop-codon readthrough is observed in a variety of organisms, from bacteria to eukaryotes, and plays a role in producing different protein isoforms. In some cases, readthrough is a programmed event that generates essential proteins with dual functions. For example, in certain viruses, readthrough is used to produce structural proteins or enzymes necessary for their replication. In eukaryotes, readthrough can contribute to protein diversity, allowing for a single gene to encode multiple protein products with distinct physiological roles. While often a controlled mechanism, it can also occur spontaneously and contribute to cellular protein variation.