BSCI 331: Exam 3 - Common DNA-Binding Motifs

Helix-turn-helix motif

simplest DNA-binding motifs

1

two alpha helices connected by a short unstructured stretch (“turn”) —> alpha helices right size to fit into groove of DNA for transcription

2

helices are held at specific angle by interactions between the helices

3

c-terminal recognition helix makes sequence-specific contacts in major groove of DNA

4

generally bind to DNA as symmetric dimers (head-to-head, tail-to-tail, mirrored images), where recognition helices bind to “half-sites” separated by one turn of DNA helix (ex, TTTAAA ←→ AAATTT)