The Rap1 Myb domain adopts a canonical three-helix bundle tertiary structure, with the second and third helices forming a helix-turn-helix variant motif. The function of this domain is unclear: it may either interact with DNA via an adaptor protein or it may be only involved in protein-protein interactions [1].

1: NMR structure of the hRap1 Myb motif reveals a canonical three-helix bundle lacking the positive surface charge typical of Myb DNA-binding domains. Hanaoka S, Nagadoi A, Yoshimura S, Aimoto S, Li B, de Lange T, Nishimura Y; J Mol Biol. 2001;312:167-175. PMID:11545594