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A species of bacteria can synthesize the amino acid histidine so it does not require histidine in its growth medium. A key enzyme, which we will call histidine synthetase, is necessary for histidine biosynthesis. When these bacteria are given histidine in their growth media, they stop synthesizing histidine intracellularly. Based on this observation alone, propose three different regulatory mechanisms to explain why histidine biosynthesis ceases when histidine is in the growth medium. To explore this phenomenon further, you measure the amount of intracellular histidine synthetase protein when cells are grown in the presence and absence of histidine. In both conditions, the amount of this protein is identical. Which mechanism of regulation would be consistent with this observation?


Answered 2 years ago
Answered 2 years ago
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1-\textbf{1-} Histidine might acts as corepressor that decrease the transcription of the histidine synthetase gene.

2-\textbf{2-} Histidine might acts as an inhibitor via feedback inhibition.

3-\textbf{3-} Histidine might inhibits the mRNA from encoding histidine synthetase to be translated , also histidine made a gene which encodes an antisense RNA.

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