E. coli needs amino acids to survive, and one of these amino acids is tryptophan. E. coli produce their own tryptophan that is encoded by their five genes located next to each other in what is called the trp operon. However, in the presence of tryptophan in the environment, there is no need for the bacteria to synthesize it, so the trp operon is switched "off." When the availability of tryptophan in the environment becomes too low, the trp operon is switched "on" to activate tryptophan synthesis. How does the trp repressor participate in this process?