New protein in human blood plasma, rich in proline, with lipid-binding properties.

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Abstract
A protein that binds to a lecithin-stabilized triglyceride emulsion was separated from plasma after removal of major lipoprotein classes by ultracentrifugation at density 1.21 g/ml. This protein, rich in proline, was purified to electrophoretic and immunochemical homogeneity by subsequent gel and ion-exchange chromatography. In native plasma and after purification, it exists as a large particle exceeding 106 daltons, but a single component with a MW of about 74,000 was found upon polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Although the purified protein contained very little bound lipid and was not present in the major lipoprotein classes from post-absorptive individuals, it was present in chylomicrons. Its concentration in plasma varied from 12 to 41 mg/dl and was significantly correlated with that of cholesterol in lipoproteins of very low and low density but not in those of high density.