p-2S-SMAD1/5/8 p-2S-SMAD1/5/8:SMAD4 Phospho-R-Smad1/5/8 forms a complex with Co-Smad Authored: Huminiecki, L, Moustakas, A, 2007-11-07 10:22:00 Pubmed11779505 Pubmed15350224 Pubmed8893010 Pubmed9311995 Pubmed9670020 Reactome Database ID Release 43201422 Reactome, http://www.reactome.org ReactomeREACT_12080 Reviewed: Heldin, CH, 2007--1-1- 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.