Tag: 21st amino acid

With only 25 selenoproteins encoded in the human genome, the question of which is the 21st amino acid points to a rare but essential component of life. This unique amino acid, selenocysteine, adds a fascinating layer to our understanding of protein synthesis and genetic recoding.

In 1986, the discovery that the UGA stop codon could direct the incorporation of selenium, in the form of selenocysteine, into proteins revolutionized genetics. This unique amino acid, known as selenocysteine, stands apart from the 20 standard protein building blocks due to its complex biosynthesis and crucial function in a select group of proteins.

Scientific consensus traditionally recognizes 20 standard amino acids used in protein synthesis, but the discovery of selenocysteine as a 21st genetically encoded amino acid has changed the conversation. This has led to widespread confusion over whether the 20 or 21 amino acids are essential for optimal health.