CALCIUM-DEPENDENT ASSOCIATION OF SURFACTANT PROTEIN-A WITH PULMONARY SURFACTANT - APPLICATION TO SIMPLE SURFACTANT PROTEIN-A PURIFICATION

Surfactant protein A (SP-A) is an abundant lipoprotein component of pu lmonary surfactant that plays multiple roles in surfactant homeostasis within the lung, A simple and rapid purification procedure for SP-A i s described. Purified surfactant is washed by centrifugation with Ca2 containing buffer to remove residual soluble proteins. Following the Ca2+ buffer wash, the surfactant pellet is washed in buffer containing EGTA and Mg2+ which releases the bound SPA in almost pure form. Subse quent chromatography of the SP-A on Sephacryl S-500 yields homogeneous preparations of the protein. The SP-A purified using this procedure r equires no exposure to either detergents or organic solvents to remove lipid. SP-A prepared by this new method inhibits lipid secretion from alveolar type II cells as effectively as SP-A prepared by other metho ds. In addition, the SP-A depleted surfactant produced in the first st ep of this procedure is capable of binding exogenous SP-A in a time de pendent, saturable and Ca2+ dependent manner. (C) 1996 Academic Press, Inc.