I have not yet found a good way to explain this. Fucose binds in the same binding site as arabinose and hence competes for binding, but does not lead to the arm being pulled off the DNA binding domain. Just saying that fucose binds and competes with arabinose doesn't fully explain things. Compounds that reduce the frequence of induction of cancer and which often interfere with carcinogens. Attenuation mechanism does this.
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