THE MOBILE FERROUS IRON POOL IN ESCHERICHIA-COLI IS BOUND TO A PHOSPHORYLATED SUGAR DERIVATIVE

Based on in vivo Mossbauer spectroscopy it has previously been demonst rated that the intracellular iron pool of Escherichia coli, grown in i ron deficient media supplemented with siderophores as the sole iron so urce, is dominated by a single Fe2+ and a single Fe3+ species, We have isolated the ferrous ion species and have purified it employing nativ e column PAGE, chromatography and ultrafiltration. The purified compou nd displays an M(app) of 2.2 kDa and an extremely low isoelectric poin t (pI) of 1.05. It is shown that this ferrous ion binding compound is neither a protein nor a nucleotide, rather it is composed mainly of ph osphorylated sugar derivatives. This compound binds approximately 40% of the cytoplasmic iron. Therefore it is proposed that this oligomeric ferrous carbohydrate phosphate represents the long sought after mobil e, low molecular mass iron pool.