NONMUSCLE MYOSIN IIA COPURIFIES WITH CHLORIDE CHANNEL-ENRICHED MEMBRANES FROM EPITHELIA

Hydrophobic affinity chromatography can be used to isolate, from bovin e tracheal epithelial cells, an intracellular membrane vesicle fractio n enriched in a single type of chloride channel. The intracellular ori gin of these vesicles and the function of this chloride channel has no t been established. As a first step in this direction, we have purifie d a 200 kDa protein that copurifies with these membranes. Partial amin o acid sequencing and immunoblotting with specific antibodies identify this protein as nonmuscle myosin IIA. Since the vesicle chloride chan nel is present in plasma membrane fractions as well, we hypothesize th at these vesicles represent an intracellular storage or recycling comp artment for epithelial chloride channels, which translocate to the pla sma membrane during periods of peak demand for epithelial fluid secret ion. (C) 1997 Academic Press.