Question

What are sequence-specific transcription factors and how does their structure (e.g., zing- finger, helix-loop-helix, leucine zipper motifs) affect their function?

Answer 1

Sequence specific transcription factors contains specific structural domains that bind to specific sequences on the DNA.The sequences on the DNA could be a promoter or enhancer sequence.When there is a change in the conformation, or three-dimensional structure of a transcription factor, it will lead to DNA binding. For example, the two loops in a transcription factor called NFATC1 that interact with DNA is found to be present in different conformations, depending on whether NFATC1 is in a form of complex with DNA or not.Moreover, it is the structure of different transcription families that results in specific areas in these protein complexes to interact with the DNA recognition motif. The recognition motif is mostly about 6 to 10 base pairs long. There are some transcription factors that have specific DNA-binding motifs such as the  basic helix-loop-helix (bHLH) structure that recognizes a specific sequence of DNA and it works in a manner that it sits on the DNA like a train car on a track. One example of such transcription factor is is the transcription factor  MyoD.