Exostosin-1 is a protein that in humans is encoded by the EXT1 gene.
This gene encodes one of the two endoplasmic reticulum-resident type II transmembrane glycosyltransferase â the other being EXT2 â which are involved in the chain elongation step of heparan sulfate biosynthesis. Mutations in this gene cause the type I form of multiple exostoses.
EXT1 has been shown to interact with TRAP1.