23. Which of the following descriptions is not correct? (A) The leucine zipper motif is important for protein-DNA interaction. (B) Ribozymes are RNA molecules with catalytic activity. (C) The poly( A ) tail can stimulate recruitment of the 40s ribosomal subunit to mRNA； therefore, it is important in initiation of protein synthesis. (D) Diphtheria toxin can inhibit mammalian RNA synthesis by reduction the elongation factor-2 activity. (E) The suppressor tRNA molecules are capable of suppressing missense mutations.