trp

Trp is the three-letter abbreviation for the amino acid tryptophan. It is one of the 20 standard amino acids and features an indole-containing aromatic side chain. Tryptophan is an essential amino acid in humans, meaning it cannot be synthesized in sufficient amounts and must be obtained through the diet.

Biological role and metabolism: Tryptophan is incorporated into proteins during translation. It serves as a precursor to several important molecules, including serotonin and melatonin in the nervous system, and niacin (via the kynurenine pathway). Dietary sources high in tryptophan include poultry, eggs, dairy products, nuts, seeds, soy, and certain grains.

Biosynthesis and genetics: In plants, fungi, and many bacteria, tryptophan is synthesized from chorismate through the tryptophan biosynthetic pathway, beginning with anthranilate. Humans lack sufficient biosynthetic capacity, reinforcing its status as an essential dietary amino acid.

Codons and translation: In the genetic code, tryptophan is encoded by a single codon, UGG. The corresponding tRNA has the anticodon CCA. Because it is specified by a single codon, tryptophan incorporation during protein synthesis is unique among amino acids.

Trp operon (bacterial regulation): The tryptophan biosynthesis operon, commonly named trp, includes structural genes trpE, trpD, trpC, trpB, and trpA and is regulated by the TrpR repressor. When tryptophan levels are high, TrpR bound to tryptophan binds to the operator to repress transcription. Additionally, an attenuation mechanism via the leader peptide gene trpL modulates transcription termination depending on tryptophan availability.