Fig. 5
From: Rare but specific: 5-bp composite motifs define SMAD binding in BMP signaling
Back-to-back binding of BMP-sensitive SMADs: a SMAD-MH1 docked to GC-SBE/SBE and GC-SBE/GC-SBE composite motifs in back-to-back binding mode. As both SMAD1 and SMAD4-MH1 bind pGC-SBE and SBE motifs, the shown binding mode is just one representative model. It is equally likely that SMAD4-MH1 binds to the pGC-SBE and SMAD1-MH1 to the SBE motif. b Model of a trimeric SMAD5/5/4 complex binding to an ID-like composite motif on one dsDNA strand and a second GC-SBE motif at another locus. SMAD5-MH1 (dimer, green, PDB: 6FZS) and the SMAD4-MH1 (orange, PDB: 5MEY) were superimposed to docked SMAD1-MH1 and SMAD4-MH1 from a. The view highlights that the limiting factor determining binding to target motifs of BMP-sensitive SMAD complexes must be the structure of the dimeric/trimeric MH2 domains