Elastin sub-fraction as binding site for lipids.

Elastin preparations were isolated from human thoracic aorta, from atherosclerotic and from grossly normal regions. A relatively mild procedure was used to avoid hot alkaline extraction and autoclaving. The elastase digest of the aortic elastin was chromatographed on a Sephadex G-100 column and separated into two fractions: A (larger molecular weight) and B (smaller molecular weight). The ratio of fraction A to total aortic elastin increased with age and the development of the atherosclerosis. Amino acid and sugar analyses showed that fraction A consistently contained more polar amino acids, hexose, hexosamine and L-fucose, and less sialic acid, in comparison with fraction B. Part of the elastin preparation was incubated with human low-density lipoprotein; a considerable amount of lipid, especially cholesterol, was transferred from the lipoprotein to the elastin. Estimation of protein and cholesterol in fractions A and B of the elastase hydrolyzate of incubated elastin showed that most of the cholesterol taken up by elastin had been in fraction A. The increased proportion of fraction A in aortic elastin derived from plaque areas appeared responsible for the marked lipid-binding capacity of plaque elastin.