A novel lipoprotein from Oomycete fungi

Abstract

This work reports on the presence of an endogenous lipoprotein in Lagenidium giganteum and Phytophthora cinnamomi as well as from the related non-sterol-deficient Oomycete species Lagenidium callinectes, and Zoophagus insidians. The lipoproteins comprise 0.2-1.0% of the total cell protein and are easily extracted with 0.2% Tween-80. The lipoprotein is homogeneous following heparin-agarose chromatography and nondenaturing gel electrophoresis. This holoprotein from all species had a molecular mass of 320,000 Da and contained four identical protein subunits of molecular mass 40,600. The lipoprotein exhibited similar physical characteristics to human low-density lipoprotein (LDL) as it comigrated with LDL on agarose gels, coeluted with LDL from heparin-agarose columns, and had a similar buoyant density of 1.006-1.063 g/cm 3. The associated lipids varied quantitatively by species and included dolichol, diglycerides, and phospholipids. The lipoproteins from sterol-deficient species bound exogenous cholesterol without displacement of any of the native lipids of the lipoprotein.