Enhances the activity of the UidB (GusB) glucuronide transporter, on its own however it has no transport activity. Glucuronide transport does not occur in strain K12 due to a variant at position 100 of the UidB (GusB, AC P0CE44, AC P0CE45) protein. In the presence of glucuronides. Belongs to the outer membrane porin (Opr) (TC 1.B.25) family. Truncated N-terminus.