E3 ubiquitin-protein ligase SMURF1 is an enzyme that in humans is encoded by the SMURF1 gene.

This gene encodes a ubiquitin ligase that is specific for receptor-regulated SMAD proteins in the bone morphogenetic protein (BMP) pathway. This protein plays a key roll in the regulation of cell motility, cell signalling, and cell polarity. Alternative splicing results in multiple transcript variants encoding different isoforms.[provided by RefSeq, Dec 2010].
Function: E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Interacts with receptor-regulated SMADs specific for the BMP pathway, SMAD1 and SMAD5, in order to trigger their ubiquitination and degradation and hence their inactivation. Promotes ubiquitination and subsequent proteasomal degradation of TRAF family members.