Iron binding proteins and their roles in the tobacco hornworm,Manduca sexta (L.)

Abstract

Manduca sexta larvae accumulate large amounts of iron during their larval feeding period. When 59Fe was fed to 5th instar larvae, it was evenly distributed among the hemolymph, gut and carcass until the cessation of feeding. By pupation 95% of the labelled iron was found in the fat body. In the adult a significant portion of this iron was found in flight muscle. Studies of the hemolymph disclosed two iron-containing proteins. The first was composed of a single polypeptide chain of 80 kD, containing one atom of iron. This protein bound ionic iron in vitro and was able to transfer this iron to ferritin when incubated with fat body in vitro. Therefore, it appeared to serve a transport function. The second protein had a molecular weight of 490 kD with subunits of 24 and 26 kD and contained 220 micrograms of iron/mg protein. Its chemical and ultrastructural characteristics were those of ferritin. These studies demonstrate the presence of both a transport protein and a unique circulating ferritin in Manduca sexta, the latter serving a storage function during development and possibly also a transport function.

Immunolocalisation of theD. melanogaster NramphomologueMalvolioto gut and Malpighian tubules provides evidence thatMalvolioandNramp2are orthologous

“…These data were supportive of an analogous mechanism for the acquisition of divalent cations from the gut lumen for both flies and mammals. Interestingly, Mvl is also expressed in the Drosophila fat body, an organ that has been shown to play a role in iron uptake, storage and release back into the haemolymph in insects (Huebers et al, 1988). Since the release of the entire D. melanogaster genome sequence, it has become clear that whereas many genes involved in iron homeostasis are conserved between insects and vertebrates, many are not, indicating important differences in their metabolism of iron (Nichol et al, 2002).…”

Multicopper oxidase-1 is a ferroxidase essential for iron homeostasis in Drosophila melanogaster

“…Insect ferritin is present in the endoplasmic reticulum and Golgi complex of a variety of cell types, including midgut cells, and iron-loaded ferritin is secreted into the hemolymph and is thought to transport iron to other parts of the body (9). Insect transferrin is present in the hemolymph, and, like mammalian transferrin, it may function as an iron transport protein (10,11), although the mechanism of ferrictransferrin uptake is unknown (12). We wondered whether iron metabolism in insects requires the activity of a multicopper ferroxidase.…”

Photobactin: a Catechol Siderophore Produced by Photorhabdus luminescens , an Entomopathogen Mutually Associated with Heterorhabditis bacteriophora NC1 Nematodes

“…Larval stages of the tobacco hornworm, Manduca sexta, contain a ferritin-type iron binding protein in the hemolymph (26,38). One mechanism that bacteria use to acquire iron from eukaryotic hosts is to produce siderophore molecules that have high affinity for iron and form soluble iron complexes to sequester and transfer ferric iron into the bacterial cells (for reviews, see references 16, 37, and 43).…”