Members of this family, which are predominantly found in the yeast protein rap1, assume a secondary structure consisting of a three-helix bundle and an N-terminal arm. They contain an Arg-Asp-Arg-Lys sequence that interacts with an ACACC region in the 3' region of the DNA-binding site [1].

1: The crystal structure of the DNA-binding domain of yeast RAP1 in complex with telomeric DNA. Konig P, Giraldo R, Chapman L, Rhodes D; Cell. 1996;85:125-136. PMID:8620531