Partial purification and characterization of phosphatidylcholine-binding proteins from rat lung lavage

Abstract

In lung lavage of rats, proteins are found which have an affinity to phosphatidylcholine, the main constituent of pulmonary surfactant. These proteins can be enriched to such an extent that SDS-gel electrophoresis reveals a characteristic banding and contaminating proteins are widely separated. The binding of these proteins to [ methyl- 14C] phosphatidyl choline is strictly pH dependent (pH 7.5, 9.5, and 10.5). The binding capacity to [ 14C]PC is significantly reduced for RCOOH derivatives of the native proteins. The proteins indicated a tendency for polypeptide aggregation/disaggregation, caused by altered ionic strength of the buffer. Immunofluorescence studies showed that these proteins lie along the alveolar membrane. It is concluded that these proteins contribute to the pulmonary surfactant complex; the physiological role of these proteins is, however, far from clear.