UPK2 is one of the proteins of the highly urothelium-specific integral membrane proteins of the asymmetric unit membrane which forms urothelium apical plaques in mammals. The asymmetric unit membrane is believed to strengthen the urothelium by preventing cell rupture during bladder distention. This protein is expressed in the peripheral blood of bladder cancer patients with transitional cell carcinomas. Recombinant human UPK2 protein, fused to His-tag at N-terminus, was expressed in E.coli.