Terminatsioonijärk

Terminatsioonijärk refers to the termination sequence in molecular biology, specifically the process by which protein synthesis (translation) is brought to an end. This process occurs when the ribosome encounters one of three specific codons on the messenger RNA (mRNA) molecule. These codons are known as stop codons: UAA, UAG, and UGA.

Unlike codons that specify amino acids, stop codons do not code for any amino acid. Instead, they are recognized by proteins called release factors. These release factors bind to the ribosome at the stop codon. The binding of the release factor triggers a series of events that lead to the dissociation of the ribosomal subunits, the release of the newly synthesized polypeptide chain (protein), and the termination of translation.

The accuracy of termination is crucial for producing functional proteins. If translation continues beyond a stop codon, it can result in a non-functional or even harmful polypeptide. Conversely, premature termination at a different codon can lead to truncated proteins that may lack essential functions. Therefore, the precise recognition of stop codons by release factors ensures the accurate completion of protein synthesis. The specific stop codons and the mechanisms of release factor binding are conserved across many organisms, highlighting the fundamental importance of this process in all living cells.