Question

Which DNA binding domain is seen in region 4.2 of sigma factor?

(a) Zinc fingers

(b) Helix turn helix

(c) Leucine zipper

(d) Beta barrel

This question was posed to me in an interview.

This is a very interesting question from Transcription in Prokaryotes : Sigma Factor in section Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

The correct answer is (b) Helix turn helix

Best explanation: Region 4.2 of sigma subunit has a helix turn helix motif that helps it to bind to the major groove of DNA. The similar motif has been seen in region 3 as well. Zinc fingers and leucine zipper are examples of other DNA binding motif.