Anti-SMAD3 antibodies are used in the immunodetection of the protein SMAD family member 3. In humans, the canonical protein has a reported length of 425 amino acid residues and a mass of 48.1 kDa. Its subcellular localization is in the nucleus and cytoplasm. Up to 4 different isoforms have been reported for this protein. It is notably widely expressed in many tissue types. A member of the Dwarfin/SMAD protein family, SMAD3 is a known receptor-regulated SMAD (R-SMAD) that is an intracellular signal transducer and transcriptional modulator activated by TGF-beta (transforming growth factor) and activin type 1 receptor kinases. Post-translational modifications have been described, including ubiquitination, acetylation and phosphorylation. The SMAD3 gene has been associated with the disease, Colorectal cancer. Synonyms for this target antigen include HsT17436, JV15-2, LDS1C, LDS3, MADH3, hMAD-3, hSMAD3, and HSPC193. SMAD3 gene orthologs have been reported in the mouse, rat, bovine, frog, chimpanzee and chicken species.