[Term] id: PR:000000027 name: smad protein def: "A protein with core domain composition consisting of one MH1 domain (Pfam:PF03165) at the N terminus and one MH2 domain (Pfam:PF03166) at the C-terminus, separated by a non-conserved linker region. Smad proteins are mediators of signal transduction in transforming growth factor beta (TGF-beta) superfamily pathways." [PRO:CNA] comment: Category=family. xref: PIRSF:PIRSF037286 is_a: PR:000000001 ! protein