Tryptophan acts as
Tryptophan acts as co-repressor, small-molecule partner that completes repressor functionality, not inducer. Aporepressor alone cannot efficiently block transcription because DNA-binding domains oriented suboptimally. Binding of two L-tryptophan molecules per dimer into hydrophobic core supplies extensive hydrophobic and hydrogen-bond interactions that reposition helix-turn-helix motifs enabling direct major groove contacts with operator palindromic bases and phosphate backbone. Rising intracellular tryptophan pool thus directly signals metabolic sufficiency, converting inactive aporepressor i
Ref: BenchChem Trp operon regulation – tryptophan binds TrpR activating repressor to block transcription.
