Catalyzes the transfer of sulfate to the C2-position of selected hexuronic acid residues within the maturing heparan sulfate (HS). 2-O-sulfation within HS, particularly of iduronate residues, is essential for HS to participate in a variety of high-affinity ligand-binding interactions and signaling processes. Required for metanephric development of kidney formation, suggesting that 2-O-sulfation within HS is essential for signaling between ureteric bud and metanephric mesenchyme. Mediates 2-O-sulfation of both L-iduronyl and D-glucuronyl residues. Homotrimer (By similarity). Interacts with the C5-epimerase GLCE. Widely expressed. Expressed at higher level in lung and brain. Weakly expressed in spleen. At 7.5 dpc, it is expressed in all three germ layers, although it appears to be more expressed in the embryonic ectoderm and the node. Widespread expression persists at 8.5 dpc, although it is clearly expressed at higher level in rhombomeres 2 and 4 and branchial arches 1 and 2 (which are populated by neural crest from these rhombomeres). At 10.5 dpc, the dorsal and ventral aspects of the neural tube, brain and midbrain-hindbrain junction show the most intense expression. A day later in development, elevated expression is found in the floor plate and the sclerotome. At 12.5 dpc, both the floor plate and the roofplate exhibit strong expression as the mesenchyme of the limb and of the developing whisker follicles. At 13.5 dpc, it is predominantly expressed in embryonic mesenchyme, especially at sites of epithelial-mesenchymal interactions such as the developing teeth and whisker follicles. Strong expression is also apparent in the perichondria of the cartilaginous skeleton, an important site for the regulation of skeletal differentiation. N-glycosylated. Mice die in the neonatal period, exhibiting bilateral renal agenesis and defects of the eye and the skeleton. Uronate 2-O-sulfates are not detected in such mice, however, the domain structure of the HS is conserved, due to a compensatory increase in N- and 6-O-sulfation maintain the overall charge density. Belongs to the sulfotransferase 3 family.