Question

You isolate a new drug that seems to kill bacteria. To understand the mechanism of the bacterial death, you do two experiments where you grow the bacteria in the presence of either radiolabeled methionine or radiolabeled uracil and then resolve the proteins or RNA as appropriate. Although the signal for the radiolabeled RNA stays constant in both treated and untreated samples, the amount of radiolabeled proteins is reduced in the treated sample.

A. Hypothesize how the drug is killing the bacteria.

B. After doing further experiments, you find that the drug has a very high affinity for the RNA sequence 5’-ACCUCC. Would you use this drug to treat human patients? Explain your answer.

Answer 1

Answer: A.

Since there is no change in the radiolabeled RNA in both drug-treated and untreated samples, there is no inhibition in RNA synthesis. In other words, transcription is not inhibited by the drug. On the other hand, it is noticed that there is a reduction in the quantity of radiolabeled protein in drug-treated samples and not in drug untreated samples. This indicates that there is some problem in the translation level. It can be stated that the drug interferes with translation of mRNA to active protein.

Answer B:

It is given that the drug has more affinity for the RNA sequence 5'-ACCUCC-3' site. According to literature, this site is important for the formation of the complex between mRNA and 30s subunit of the ribosome. We all know that the 30S subunit of the ribosome is essential for initiation of translation event. Thus, binding of the to this RNA sequence will inhibit the formation of the above-mentioned complex and thus translation of the protein will be inhibited thereby leading to reduction in the quantity of protein formed.