Sulfotransferase that utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) to catalyze the transfer of a sulfo group to an N-unsubstituted glucosamine linked to a 2-O-sulfo iduronic acid unit on heparan sulfate (PubMed:9988768). Catalyzes the O-sulfation of glucosamine in GlcA2S-GlcNS (PubMed:9988768). Unlike HS3ST1/3-OST-1, does not convert non-anticoagulant heparan sulfate to anticoagulant heparan sulfate (PubMed:9988768). 3'-phosphoadenylyl sulfate + alpha-D-glucosaminyl-[heparan sulfate](n) = 3-sulfo-alpha-D-glucosaminyl-[heparan sulfate](n) + adenosine 3',5'-bisphosphate + H(+) Highly expressed in the brain and weakly expressed in the heart, placenta, lung and skeletal muscle. Belongs to the sulfotransferase 1 family.