[Term]
id: GO:0071141
name: SMAD protein complex
namespace: cellular_component
def: "A protein complex that consists of only SMAD proteins; may be homomeric or heteromeric. Heteromeric complexes act as transcription factors while homomeric complexes exist but are transcriptionally inactive. Hetero- versus homotrimerization is largely enthalpy driven." [GOC:bhm, GOC:mah, PMID:9670020]
synonym: "SMAD complex" EXACT [GOC:mah]
is_a: GO:0032991 ! protein-containing complex