SMAD2 or Mothers against decapentaplegic homolog 2 is a polypeptide that, as its name describes, is a homolog of the Drosophila gene: "Mothers against decepentaplegic". It belongs to the SMAD family of proteins, which belong to the TGF-Beta superfamily of modulators. Like many other TGF-Beta family members SMAD2 is involved in cell signalling. SMAD2 modulates signals of activin and TGF-Beta's. It interacts with SMAD anchor for receptor activation (SARA). The binding of ligands causes the phosphorylation of the SMAD2 protein and the dissociation from SARA and the association with SMAD4. It is subsequently transferred to the nucleus where it forms complexes with other proteins and acts as a transcription factor. SMAD2 is a receptor regulated SMAD (R-SMAD) and is activated by bone morphogenetic protein type 1 receptor kinase.

This antibody is cross reactive with Smad3.