E3 ubiquitin-protein ligase that acts as a negative regulator of BMP signaling pathway. Mediates ubiquitination and degradation of SMAD1 and SMAD5, 2 receptor-regulated SMADs specific for the BMP pathway. Promotes ubiquitination and subsequent proteasomal degradation of TRAF family members and RHOA. Promotes ubiquitination and subsequent proteasomal degradation of MAVS (PubMed:23087404). Acts as a positive regulator of smoothened signaling pathway by mediating ubiquitination of PTCH1, leading to endocytosis and lysosomal degradation of PTCH1 (By similarity). Acts as an antagonist of TGF-beta signaling by ubiquitinating TGFBR1 and targeting it for degradation (PubMed:21791611). Plays a role in dendrite formation by melanocytes (PubMed:23999003). {ECO:0000250|UniProtKB:Q9CUN6, ECO:0000269|PubMed:10458166, ECO:0000269|PubMed:19937093, ECO:0000269|PubMed:21402695, ECO:0000269|PubMed:21791611, ECO:0000269|PubMed:23087404, ECO:0000269|PubMed:23999003}. This is the function of SMURF1 (SMAD specific E3 ubiquitin protein ligase 1, ENSG00000198742).