Influence of Iron Deprivation on the Membrane Composition of Anacystis nidulans

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Abstract
Cultures of A. nidulans were grown under Fe deficient conditions and then restored by the addition of Fe. Membrane proteins from Fe-deficient and Fe-restored cells were analyzed by lithium dodecyl sulfate-polyacrylamide gradient gel electrophoresis. The incorporation of [35S]sulfate into membrane proteins and lactoperoxidase-catalyzed 125I iodination were used to monitor the rates of polypeptide biosynthesis and surface exposure of membrane proteins, respectively. These polypeptide profiles revealed major differences in the membrane composition of Fe-deficient and normal cells. Fe deficiency caused a decrease in the amount of certain important membrane proteins, reflecting a decreased rate of biosynthesis of these peptides. Several photosystem II peptides also showed an increase in surface exposure after Fe stress. In addition, Fe deficiency led to the synthesis of proteins at 34 and 52 kilodaltons which were not present in normal cells. When Fe was restored to a deficient culture, a metabolic sequence was initiated within the first 12 h after the addition of Fe which led to phenotypically normal cells. Pulse labeling with [35S]sulfate during this period demonstrated that Fe addition initiates a coordinated pattern of synthesis that leads to the assembly of normal membranes.