ANALYSIS OF IRON-BINDING COMPONENTS IN THE LOW-MOLECULAR WEIGHT FRACTION OF RAT RETICULOCYTE CYTOSOL

1. Rat reticulocytes were incubated with rat 125I-Tf59Fe under conditions inhibiting heme synthesis. 2. Cytosol, prepared from the reticulocytes, was separated and analysed by gel filtration and Amicon Ultrafiltration. An iron-containing low molecular weight fraction derived from the cytosol was further analysed by HPLC size-exclusion chromatography and HPLC reversed phase chromatography. 3. Conditions inhibiting heme synthesis and uncoupling the oxidative phosphorylations lead to a large increase in the Fe-containing low molecular weight fraction in the cytosol. 4. The components in the low molecular weight fraction have an apparent molecular weight of 5500 Dalton as determined with HPLC size-exclusion chromatography. 5. The low molecular weight fraction contained several iron chelating components like glycin, 1/2 cystine and citrate, but no specific iron-binding proteins, nucleotides or pyrophosphate.