Question:
Lac repressor of E. coli contains ________ DNA binding motifs.
Lac repressor of E. coli contains ________ DNA binding motifs.
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Prokaryotic repressors (like Lac and Lambda) typically use HTH motifs.
Updated On: May 14, 2026
- Helix turn helix
- Helix loop helix
- Leucine zipper
- Zinc finger
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The Correct Option is A
Solution and Explanation
Step 1: Concept
DNA-binding proteins use specific structural motifs to recognize and bind to operator sequences in the DNA.
Step 2: Meaning
The Lac repressor is a protein that inhibits the expression of the lac operon by binding to the lac operator.
Step 3: Analysis
Structural studies of the Lac repressor have shown that its N-terminal domain contains a classic Helix-Turn-Helix (HTH) motif. This motif consists of two alpha-helices joined by a short turn, where one helix (the recognition helix) fits into the major groove of the DNA. Helix-loop-helix and Leucine zippers are more common in eukaryotic transcription factors.
Step 4: Conclusion
The Lac repressor utilizes the Helix-Turn-Helix motif for DNA interaction. Final Answer: (A)
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