TGFBR1, Transforming growth factor, beta receptor I is a TGF beta receptor. TGFBR1 is its human gene. The protein encoded by this gene forms a heteromeric complex with type II TGF-beta receptors when bound to TGF-beta, transducing the TGF-beta signal from the cell surface to the cytoplasm. The encoded protein is a serine/threonine protein kinase. Mutations in this gene have been associated with Loeys-Dietz aortic aneurysm syndrome (LDAS). TGFB1 regulates cell cycle progression by a unique signaling mechanism that involves its binding to TGFBR2 and activation of TGFBR1. Both are transmembrane serine/threonine receptor kinases. The TGFBR1 receptor may be inactivated in many of the cases of human tumor cells refractory to TGFB-mediated cell cycle arrest. Vellucci and Reiss (1997) reported that the TGFBR1 gene is approximately 31 kb long and contains 9 exons. The organization of the segment of the gene that encodes the C-terminal portion of the serine/threonine kinase domain appears to be highly conserved among members of the gene family.