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Ferritin and Sideroblastic Anaemias: Inhibition of Protein Synthesis by Protease Contaminants in Commercial Preparations of Ferritin
Author(s) -
Freedman Michael L.,
Cohen Howard S.,
Rosman Judith,
Forte Frank J.
Publication year - 1976
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1976.tb00962.x
Subject(s) - ferritin , protease , chemistry , biochemistry , hemoglobin , biology , microbiology and biotechnology , enzyme
Commercial preparations of ferritin inhibited reticulocyte‐lysate cell‐free protein synthesis and disaggregated polyribosomes to monoribosomes and ribosomal subunits. These effects were prevented by addition of reduced glutathione (GSH) to the incubation medium, but ferritin did not lower GSH concentration in the lysates. The more purified the ferritin preparation, the less inhibition of protein synthesis was observed. These data suggested that the effect was due to a contamination of the ferritin with proteolytic activity. In confirmation of this proposal we demonstrated that there was protease activity in both the 2 × and 5 × crystallized ferritin preparations, with 2.5 times greater activity in the 2 × preparation. The proteolytic activity in ferritin was inhibited by incubation with the protease inhibitor tosyl lysine chloromethyl ketone (TLCK). When an amount of trypsin equivalent to the protease activity of the ferritin was added to the incubation mixture, similar effects on protein synthesis and the ribosome‐polyribosome component were found. Both GSH and TLCK prevented these effects of trypsin. These data suggest that the previously reported effect of ferritin on reticulocyte cell‐free protein synthesis was due to contamination of the ferritin by a protease. It appears that ferritin does not play a direct role in the pathogenesis of sideroblastic anaemias.