The silkgland-specific transcription factor FMBP-1 from the silkworm Bombyx mori contains a unique DNA-binding domain of four tandem STPRs, namely the score and three amino acid peptide repeats [1]. In the presence of target DNA, STPRs adopts a zig-zag structure of three or four tandem alpha-helices that run along the major groove of DNA [1].

1: Structures of an all-alpha protein running along the DNA major groove. Yu LY, Cheng W, Zhou K, Li WF, Yu HM, Gao X, Shen X, Wu Q, Chen Y, Zhou CZ; Nucleic Acids Res. 2016;44:3936-3945. PMID:26939889