By forming a complex with tryptophan-activated TRAP, and masking its RNA binding site, it inhibits TRAP's RNA binding ability, thereby abolishing TRAP regulation of gene expression, leading to antitermination and increased trp operon expression. AT acts by competing with messenger RNA for the RNA binding domain of TRAP. Homopentamer or homohexamer. By uncharged Trp tRNA, via the T-box transcription antitermination mechanism.