UniProt Summary: Sulfotransferase that utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) to catalyze the transfer of a sulfo group to heparan sulfate. The substrate-specific O-sulfation generates an enzyme-modified heparan sulfate which acts as a binding receptor to Herpes Simplex Virus-1 (HSV-1) and permits its entry. Unlike 3- OST-1, does not convert non-anticoagulant heparan sulfate to anticoagulant heparan sulfate. {ECO:0000269|PubMed:15303968}.