UPK3A belongs to the uroplakin-3 family. Uroplakins (UP) are key components of the urothelium. They are transmembrane proteins that pass the lipid bilayer once (UPII, UPIIIa, and UPIIIb) or four times (UPIa and UPIb; both belonging to the 'tetraspanin' family). All have large luminal/extracellular domains, but only UPIIIa and UPIIIb have significant cytoplasmic portions in their C-termini. UPK3A is a highly specific and moderately sensitive immunohistochemical marker for primary and metastatic urothelial carcinomas. Mutations in this gene may be associated with renal adysplasia Recombinant human UPK3A protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by conventional chromatography, after refolding of the isolated inclusion bodies in a renaturation buffer.