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. Homotrimer. Expressed in heart, limb, head and trunk. At stages 20 and 24, it is expressed in the most regions of the first and second pharyngeal arche. In both wing and leg buds, it is detected at the overlying ectoderm and mesenchyme throughout stages 21, 23 and 24. Belongs to the sulfotransferase 3 family.