stopkoodoni

Stopkoodoni is a term occasionally used in biology glossaries to denote the sequence element that terminates protein synthesis during translation. In standard genetics, termination is governed by stop codons in messenger RNA—UAA, UAG, and UGA—recognized by release factors that catalyze the release of the completed polypeptide and the disassembly of the ribosome. The term stopkoodoni is not universally adopted; it appears mainly in educational or speculative contexts as an alternative label for these termination signals.

Function and recognition of stopkoodoni vary across domains of life. In bacteria, release factor RF1 recognizes UAG and UAA, while RF2 recognizes UGA and UAA. In eukaryotes, a single release factor, eRF1, recognizes all three stop codons and works with the GTPase eRF3 to terminate translation. Mitochondria and certain organelles can employ slightly different codon usages and release factor repertoires, reflecting deviations from the universal code.

Variations and exceptions are part of the stopkoodoni landscape. Translational readthrough can occur when near-stop codons are suppressed, allowing incorporation of amino acids beyond the canonical stop. Selenocysteine and, in some organisms, pyrrolysine insertion can convert specific stop codons into signals for incorporating nonstandard amino acids under programmed contexts.

Applications and significance extend to research and biotechnology. Expanding or reassigning stopkoodoni through genetic code engineering enables incorporation of noncanonical amino acids, design of specialized proteins, and refined control of gene expression. The concept remains chiefly of educational and theoretical interest, illustrating how termination signals shape proteome composition and evolutionary adaptation.

See also: stop codon, translation termination, nonsense mutation, genetic code expansion.