Biochemical studies on the isolation and characterization of human spleen haemosiderin

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Abstract
Hemosiderin was isolated from thalassemic human spleens by centrifugation through concentrated KI solutions. A method for solubilizing hemosiderin was developed which leaves the iron oxyhydroxide cores and constituent polypeptides intact, facilitating furhter purification and analysis. Purified hemosiderin contained no detectable heme, trace amounts of carbohydrate, and iron and phosphorus in a molar ratio of 6:1; much of the phosphate may be present as core-adsorbed. Several lipids were present, but it is not certain whether these are contaminants or components of the hemosiderin granules. In all preparations examined, a characteristic group of 6-7 peptides of apparent MW 12,900-17,800 were found, with a major band at MW 14,500 and, in addition, a minor component of MW 42,000; these peptides co-chromatographed with the cores. Negatively stained electron micrographs suggest that these peptides from an incomplete shell about the cores, consistent with the view that hemosiderin is a proteolytic product of ferritin.