ISOLATION AND PARTIAL CHARACTERIZATION OF 2 PORCINE SPLEEN FERRITIN FRACTIONS WITH DIFFERENT ELECTROPHORETIC MOBILITY

Ferritin isolated from porcine spleen could routinely be separated in two fractions on nondenaturating gradient gels. Both fractions could b e isolated with a purity of 96% when applied to two serially linked co lumns, each 200 cm in length, packed respectively with Sepharose 4B an d Sepharose 6B. Both fractions were similar as judged by electron micr oscopy. Assessed biochemically fractions were equal with respect ro su bunit composition, iron and phosphorus content, as well as amino acid composition (with the exception of N-acetylglucosamine). Carbohydrate analysis showed that the fraction with an apparent mass of 440 kDa (=F FL) contained 1.8% (w/w) glycans, whereas the fraction with an apparen t mass of 670 kDa (=FFH) contained nearly five times as much (neutral) sugar residues (8.9%, w/w) and 10 times as much sialic acid. This dif ference in amount of carbohydrate side chains might explain the dissim ilarity in electrophoretic mobility of the two fractions.