Vascular endothelium glycoprotein that plays an important role in the regulation of angiogenesis (PubMed:21737454, PubMed:23300529). Required for normal structure and integrity of adult vasculature (PubMed:7894484). Regulates the migration of vascular endothelial cells (PubMed:17540773). Required for normal extraembryonic angiogenesis and for embryonic heart development (By similarity). May regulate endothelial cell shape changes in response to blood flow, which drive vascular remodeling and establishment of normal vascular morphology during angiogenesis (By similarity). May play a critical role in the binding of endothelial cells to integrins and/or other RGD receptors (PubMed:1692830). Acts as TGF-beta coreceptor and is involved in the TGF-beta/BMP signaling cascade that ultimately leads to the activation of SMAD transcription factors (PubMed:8370410, PubMed:21737454, PubMed:22347366, PubMed:23300529). Required for GDF2/BMP9 signaling through SMAD1 in endothelial cells and modulates TGFB1 signaling through SMAD3 (PubMed:21737454, PubMed:22347366, PubMed:23300529). Homodimer; disulfide-linked (PubMed:8370410, PubMed:1326540, PubMed:21737454, PubMed:22347366, PubMed:28564608). Forms a heteromeric complex with the signaling receptors for transforming growth factor-beta: TGFBR1 and/or TGFBR2 (PubMed:1326540). It is able to bind TGFB1 and TGFB2 with high affinity, but not TGFB3 (PubMed:8370410, PubMed:1326540). Interacts with GDF2, forming a heterotetramer with a 2:2 stoichiometry (PubMed:21737454, PubMed:22347366, PubMed:28564608). Interacts with ACVRL1 (PubMed:22347366, PubMed:28564608). Can form a heteromeric complex with GDF2 and ACVRL1 (PubMed:28564608). Interacts with BMP10 (PubMed:21737454). Interacts with DYNLT4 (PubMed:16982625). Interacts with ARRB2 (PubMed:17540773). Detected on umbilical veil endothelial cells (PubMed:10625079). Detected in placenta (at protein level) (PubMed:1692830). Detected on endothelial cells (PubMed:1692830). The ZP domain mediates dimerization. The N-terminal OR region is composed of two intertwined domains (OR1 and OR2) with a common, novel fold. Each contains 12 beta-strands that form a parallel beta-helix-like structure, plus a single alpha-helix. The OR1 region mediates interaction with GDF2. The disease is caused by variants affecting the gene represented in this entry.