The MH1 is a small DNA-binding domain present in SMAD (small mothers against decapentaplegic) family of proteins. It binds to the major groove in an unusual manner via a beta hairpin structure. It negatively regulates the functions of the MH2 domain, the C-terminal domain of SMAD. This MH1 belongs to SMAD7, an inhibitory SMAD (I-SMAD) or antagonistic SMAD, which acts as a negative regulator of signaling mediated by TGF-beta superfamily ligands, by blocking TGF-beta type 1 and activin association with the receptor as well as access to SMAD2. SMAD7 enhances muscle differentiation, playing pivotal roles in embryonic development and adult homoeostasis. Altered expression of SMAD7 is often associated with cancer, tissue fibrosis and inflammatory diseases.
Jiyao W et al.(2023). "The conserved domain database in 2023.",