Abstract
Many lipid-binding proteins such as pleurotolysin and ostreolysin have been isolated from the edible mushroom Pleurotus ostreatus. In this study, we detected a novel lipid-binding protein with a molecular weight of 62 kDa by measuring via centrifugation the association of aqueous extracts of the mushroom with lipid vesicles composed of various phospholipids. The 62-kDa protein (p62) was purified by sedimentation of the mixture of protein extracts and acidic phospholipid-containing lipid vesicles. The purified p62 bound to phosphatidylglycerol (PG)/phosphatidylcholine/cholesterol (5:45:50) vesicles but not to vesicles composed of other phospholipids including phosphatidylserine (PS), phosphatidylinositol, phosphatidic acid, lysoPS, and lysophosphatidylinositol. The p62 protein specifically associated with the PG-containing vesicles but not with other polyglycerophospholipid vesicles consisting of cardiolipin, bis(monoacylglycero)phosphate, monolysocardiolipin, or dilysocardiolipin, suggesting that p62 recognized a precise molecular structure of PG. Intrinsic tryptophan fluorescence of p62 was changed by incubation of p62 with PG-containing vesicles. Staining of giant unilamellar vesicles with fluorescence-labeled p62 showed that p62 bound to PG-containing vesicles but not PS-containing vesicles. These observations signify the potential usefulness of p62 as a tool for studying the functions of PG molecules in biological membranes.
