Question

Which of the following is NOT true of the HTH motif of DNA-binding proteins?

• Helix 2 stabilizes the structural domain with Helix 3 through hydrophobic interactions.

• Helix 3 situated near the N-terminal of the protein is the DNA recognition helix.

• Helix 2 is the helix at the beginning of the HTH motif.

• There are 2 successive alpha helices separated by a sharp beta-turn.

Answer 1

Helix turn Helix motif is used by DNA binding proteins to bind to its target regions in the DNA. It consists of two helices linked by a sharp turn. Helix 2 on the C-terminal region involves in DNA recognition and binds to the major groove of the DNA while the first helix in the N-terminal region involves in stabilization of the interaction between the protein and DNA. The only option which satisfies the HTH motif of DNA binding proteins is option 4 - There are 2 successive alpha helices separated by a sharp beta - turn

Therefore, the options which are not true of the HTH motif of DNA binding proteins are as follows

1. Helix 2 stabilizes the structural domain with Helix 3 through hydrophobic interactions - As helix 1 involves in stabilization and there is no helix 3
2. Helix 3 situated near the N-terminal of the protein is the DNA recognition helix - There is no helix 3 in HTH motif of DNA binding proteins
3. Helix 2 is the helix at the beginning of the HTH motif - The motif starts with Helix 1 in the N-terminal region which is the beginning of the HTH motif