IndraLab

"Phosphorylation of the C-terminal serine residues in R-Smads by type I receptor kinases is a crucial step in TGF-b family signalling (Abdollah et al., 1997; Macias-Silva et al., 1996; Souchelnytskyi et al., 1997). The two most C-terminal serine residues become phosphorylated and, together with a third, non-phosphorylated serine residue, form an evolutionarily conserved SSXS motif in all R-Smads.... TGF-b and activin receptors phosphorylate Smad2 and Smad3, and BMP receptors phosphorylate Smad1, Smad5 and Smad8 (Chen et al., 1998) (Fig. 1). The consequence of R-Smad phosphorylation is the formation of oligomeric complexes with the Co-Smad, Smad4."