Drosophila melanogaster transferrin cDNA was cloned from an ovarian cDNA library by using a PCR fragment amplified by two primers designed from other ...
Eur. J. Biochem. 260, 414±420 (1999) q FEBS 1999
Drosophila melanogaster transferrin Cloning, deduced protein sequence, expression during the life cycle, gene localization and up-regulation on bacterial infection Toyoshi Yoshiga1, Teodora Georgieva1, Boris C. Dunkov1, Nedjalka Harizanova2, Kiril Ralchev2 and John H. Law1 1
The Departments of Biochemistry and Entomology and the Center for Insect Science, University of Arizona, Tucson, USA; The Department of Genetics, Faculty of Biology, Sofia University, Bulgaria
2
Drosophila melanogaster transferrin cDNA was cloned from an ovarian cDNA library by using a PCR fragment amplified by two primers designed from other dipteran transferrin sequences. The clone (2035 bp) encodes a protein of 641 amino acids containing a signal peptide of 29 amino acids. Like other insect transferrins, Drosophila transferrin appears to have a functional iron-binding site only in the N-terminal lobe. The C-terminal lobe lacks ironbinding residues found in other transferrins, and has large deletions which make it much smaller than functional C-terminal lobes in other transferrins. In-situ hybridization using a digoxigenin labeled transferrin cDNA probe revealed that the gene is located at position 17B1-2 on the X chromosome. Northern blot analysis showed that transferrin mRNA was present in the larval, pupal and adult stages, but was not detectable in the embryo. Iron supplementation of the diet resulted in lower levels of transferrin mRNA. When adult flies were inoculated with bacteria (Escherichia coli), transferrin mRNA synthesis was markedly increased relative to controls. Keywords: transferrin; Drosophila melanogaster; sequence; chromosome; expression; up-regulation; immunity.
Iron is an essential nutrient required for nearly all living organisms. Ionic iron is also toxic by virtue of its ability to catalyze the formation of membrane-destroying free radicals. Ionic iron forms oxides that are insoluble at physiological pH. Thus, in order to absorb and transport iron, most organisms have acquired special cofactors and proteins that are capable of maintaining iron in a water soluble state. Iron metabolism has been studied extensively in vertebrates. In vertebrate serum, ferric ion is transported by transferrin, a single chain polypeptide (
