STUDIES ON STRUCTURE OF FERRITIN AND APOFERRITIN FROM HORSE SPLEEN .I. TRYPTIC DIGESTION OF FERRITIN AND APOFERRITIN

1. 1. Proteolytic digestion with trypsin has been used to study the change in conformation of horse spleen apoferritin on binding of micellar iron to form ferritin. In the course of a 30-min digestion, apoferritin was cleaved to about 2.5 times the extent of ferritin. 2. 2. The products of digestion were analysed by fingerprinting and by ion-exchange chromatography, and a number of peptides, which were absent in ferritin digests, were shown to be present in apoferritin digests. 3. 3. The total number of tryptic peptides in overnight digests of apoferritin agreed well with the number of lysin plus arginine residues found by amino acid analysis. 4. 4. The further investigation of these 'difference peptides' which were found in apoferritin, but not in ferritin, digests may yield useful information regarding the nature of the binding of the iron micelle within the apoferritin protein shell. © 1969.