Purification and characterization of mycoferritin from Aspergillusflavus MTCC 873.

The fungus Aspergillus flavus MTCC 873, a non-toxigenic isolate demonstrated its capability to synthesize mycoferritin (MF) upon induction with iron in yeast extract sucrose (YES) medium. The molecular mass, yield, iron and carbohydrate contents of the MF were 440 kDa, 0.015 mg/g of wet mycelia, 0.8 and 30.4%, respectively. Native gel-electrophoresis revealed a band corresponding to dimeric form of equine spleen ferritin (ESF). Subunit analysis by SDS-PAGE revealed a single protein band with an apparent molecular mass of 24 kDa, suggesting similar sized subunits in the structure of apoferritin shell. Immunological cross-reactivity was observed with the anti-fish liver ferritin. Transmission electron microscopy (TEM) revealed an apparent particle size of 100 Å. N-terminal amino acid sequence of MF revealed a sequence of SLPLQDYA, which showed identities with other eukaryotic ferritin sequences. The spectral characteristics (UV/VIS, fluorescence and circular dichroic spectra) were similar to ESF. The fungus, unlike A. parasiticus 255 (non-toxigenic) was incapable of producing aflatoxins, when grown in YES media.

Isolation and characterization of monkey liver ferritin.

Monkey liver ferritin was isolated and purified along with human liver ferritin and their physicochemical and immunological characteristics were compared. The apparent molecular weight of monkey liver ferritin was estimated to be 430 kDa as against 450 kDa of human liver ferritin. Both ferritins appeared to be made up of a 22.5 kDa polypeptide under denaturing conditions and the proteins contained neutral sugar (wt/wt) of 2.0% (monkey) and 2.4% (human). By immunoblots both human and monkey liver ferritins showed appreciable cross-reactivity with the polyclonal antibodies raised against either proteins. Monkey liver ferritin, however, was not recognised by the human monoclonal antibody. The amino acid composition of both ferritins was more or less similar. Isoelectric focusing indicated that monkey liver ferritin showed microheterogeneity with three bands at pI 5.4, 5.5 and 5.6, whereas human liver ferritin showed a single band at pI 5.6 confirming the relative acidic nature of monkey liver ferritin.

Liver tissue injury secondary to iron overload in beta-thalassemia/hemoglobin E disease.

Liver tissues from 17 patients with advanced stages of beta-thal/Hb E disease were examined by light and electron microscopy, with emphasis on cellular damage due to excess iron overload. Various histochemical stains were performed to grade degrees of iron deposition and fibrosis, and to demonstrate hepatitis B surface antigen, in Kupffer cells as well as macrophages. The results of light and electron microscopic studies were correlated. There was a variation in the distribution of hepatic iron and the severity of fibrosis. In most of the cases ballooning degeneration of the hepatocytes, increase in number of lysosomes, hemosiderin and ferritin in hepatocytes as well as in the sinusoidal lining cells were found. The ferro-acidophilic body, representing another important form of hepatocellular necrosis also occurred. So far no precise mechanisms can be concluded.