domain:Although 2 transmembrane domains are predicted, PubMed:19269366 showed that it only contains one transmembrane domain. The other predicted transmembrane region is probably a hairpin-type region embedded into the membrane, which does not cross the membrane. It is unclear which of the 2 predicted transmembrane regions is the transmembrane or the hairpin-type region.,domain:The proline-rich region (PRD) mediates the interaction with COPII coat subunits Sec23/24.,function:Required for collagen VII (COL7A1) secretion by loading COL7A1 into transport carriers. May participate in cargo loading of COL7A1 at endoplasmic reticulum exit sites by binding to COPII coat subunits Sec23/24 and guiding SH3-bound COL7A1 into a growing carrier. Does not play a role in global protein secretion and is apparently specific to COL7A1 cargo loading. However, it may participate in secretion of other proteins in cells that do not secrete COL7A1.,similarity:Belongs to the MIA/OTOR family. Tango1 subfamily.,similarity:Contains 1 SH3 domain.,subcellular location:Localizes at endoplasmic reticulum exit sites. After loading of COL7A1 into transport carriers, it is not incorporated into COPII carriers and remains in the endoplasmic reticulum membrane.,subunit:Interacts (via SH3 domain) with COL7A1. Associates with the COPII coat subunits Sec23/Sec24.,tissue specificity:Broadly expressed, except in bone marrow and peripheral blood mononuclear cells. Down-regulated in melanoma tissue.,