ISOLATION AND PROPERTIES OF DROSOPHILA-MELANOGASTER FERRITIN - MOLECULAR-CLONING OF A CDNA THAT ENCODES ONE SUBUNIT, AND LOCALIZATION OF THE GENE ON THE 3RD CHROMOSOME

Ferritin was purified from iron-fed Drosophila melanogaster extracts b y centrifugation in a gradient of potassium bromide. On polyacrylamide gel electrophoresis, the product showed two protein bands correspondi ng to the ferritin monomer and dimer. Electrophoresis following dissoc iation with SDS and 2-mercaptoethanol revealed three strong bands of a pproximately 25, 26, and 28 kDa. N-terminal amino acid sequences were identical for the 25-kDa and 26-kDa subunits, but different for the 28 -kDa subunit. Conserved ferritin PCR primers were used to amplify a 36 0-bp cDNA product. which was used to isolate a clone from a D. melanog aster cDNA library that contained the complete coding sequence for a f erritin subunit. Additional 5' sequence obtained by the RACE method re vealed the presence of a putative iron regulatory element. The PCR pro duct was also used to locate the position of the ferritin subunit gene at region 99F on the right arm of the third chromosome. The deduced a mino acid sequence of the D. melanogaster ferritin subunit contained a signal sequence and resembled most closely ferritin of the mosquito A edes aegypti. The evolution of ferritin sequences is discussed.