. "Edited: Jassal, B, 2006-01-18 10:19:52"^^ . "Reviewed: Heldin, CH, 2006-04-18 14:26:12"^^ . "Reviewed: Huang, Tao, 2012-05-14"^^ . "Authored: Heldin, CH, Moustakas, A, Huminiecki, L, Jassal, B, 2006-02-02"^^ . "Edited: Jassal, B, 2012-04-10"^^ . "The phosphorylated C-terminal tail of R-SMAD induces a conformational change in the MH2 domain (Qin et al. 2001, Chacko et al. 2004), which now acquires high affinity towards Co-SMAD i.e. SMAD4 (common mediator of signal transduction in TGF-beta/BMP signaling). The R-SMAD:Co-SMAD complex (Nakao et al. 1997) most likely is a trimer of two R-SMADs with one Co-SMAD (Kawabata et al. 1998). It is important to note that the Co-SMAD itself cannot be phosphorylated as it lacks the C-terminal serine motif."^^ . . . . . . . . . "Phosphorylated SMAD2 and SMAD3 form a complex with SMAD4"^^ . . . . .