This Tube-Death domain has an insertion between helices 2 and 3, and a C-terminal tail compared with the Death domain of Pelle proteins in Drosophila. The two N-terminal Death domains of the serine/threonine kinase Pelle and the adaptor protein Tube interact to form a six-helix bundle fold arranged in an open-ended linear array with plastic interfaces mediating their interactions. This interaction leads to the nuclear translocation of the transcription factor Dorsal and activation of zygotic patterning genes during Drosophila embryogenesis, and is assisted by the significant and indispensable contacts in the heterodimer contributed by the insertion and C-terminal tail described above [1].

1: Three-dimensional structure of a complex between the death domains of Pelle and Tube. Xiao T, Towb P, Wasserman SA, Sprang SR; Cell. 1999;99:545-555. PMID:10589682