Purification and level of expression in bronchoalveolar lavage of a human polychlorinated biphenyl (PCB)-binding protein: evidence for a structural and functional kinship to the multihormonally regulated protein uteroglobin.

A human lung polychlorinated biphenyl (PCB)-binding protein was purified by sequential chromatography of lavage fluid incubated with the tritium-labeled, high-affinity ligand, 4,4'-bis(methylsulfonyl)-2,2',5,5'-tetrachlorobiphenyl. From sodium dodecyl sulfate polyacrylamide gel electrophoresis gradient gels, it was evident that a single band with an approximate molecular weight of 13 kD was present in the eluate from the final chromatographic step. Antibodies raised against the human lung PCB-binding protein detected a single band of corresponding size in lavage fluid in immunoblotting experiments. Furthermore, the antibodies detected significantly higher levels of the lung PCB-binding protein in lavage fluid from nonsmokers as compared to smokers. The purified protein was sequenced, and an alignment of the obtained aminoterminal amino acid residues of the human lung PCB-binding protein to uteroglobin and to a rat lung PCB-binding protein revealed an overall positional identity of approximately 45%. The amino acids suggested to participate in ligand binding of uteroglobin were extensively conserved in the PCB-binding proteins. Thus, we conclude that we have purified and raised antibodies against a human lung PCB-binding protein and that it has a structural as well as a functional kinship to the steroid-binding and multihormonally regulated rabbit protein uteroglobin.