Cystic fibrosis: molecular weight estimation of the ciliary inhibitor

The molecular weight of the ciliary inhibitor fractionated from media of cultured fibroblasts derived from cystic fibrosis patients was estimated by sucrose density gradient ultracentrifugation, membrane filtration and gel filtration. Ultracentrifugation analysis indicated a molecular weight closer to the α 1 chain of haptoglobin (9,100) than to immunoglobulin G (150,000). Molecular filtration on Amicon membranes indicated a molecular weight range of 1,000 to 10,000. Gel filtration on Sephadex G 50F indicated a molecular weight of 4,500 to 10,000. These results characterize the ciliary inhibitor from fibroblast media as a small molecular weight protein.