What makes puromycin (about its structure) a good ribosome

inhibitor (over aminoacyl - tRNA) ?

Both puromycin and the 3' end of the aminoacyl tRNA have an amino acid residue bonded to a ribose sugar.

Explanation:

The structure of puromycin resembles the 3' end of aminoacyl-tRNA. Due to its structural resemblance, puromycine is able to bind to the ribosomal A site. Puromycin participates in peptide bond formation and forms peptidyl-puromycin. The rest of the structure of puromycin does not resemble with tRNA. Therefore, after the formation of a peptide bond, there is no translocation to the P site. Rather, puromycin dissociates from the ribosome resulting in premature termination of protein synthesis.