Function: Transcriptional modulator activated by TGF-beta (transforming growth factor) and activin type 1 receptor kinase. SMAD3 is a receptor-regulated SMAD (R-SMAD) (By similarity).
Other Modifications: View all modification sites in dbPTM
Protein Subcellular Localization: Cytoplasm (By similarity). Nucleus (By similarity). Note=In the cytoplasm in the absence of ligand. Migration to the nucleus when complexed with SMAD4 (By similarity).