PURIFICATION AND CDNA CLONING OF FERRITIN FROM THE HEPATOPANCREAS OF THE FRESH-WATER CRAYFISH PACIFASTACUS-LENIUSCULUS

Ferritin was purified from the hepatopancreas of the freshwater crayfi sh Pacifastacus leniusculus after injection of iron. It has the same s ize as horse spleen ferritin (440 kDa) and migrates as two bands, 19 k Da and 20 kDa, respectively, in SDS/PAGE under reducing conditions. Cr ayFish ferritin (20 kDa) was cloned from a hepatopancreas cDNA library . The deduced amino acid sequence of the crayfish ferritin shows a clo ser relationship to vertebrate ferritin heavy chains than to insect fe rritin and contains the conserved H-specific residues for the ferroxid ase centre found in vertebrate ferritin heavy chain. An IRE(iron-respo nsive element)-like sequence with a predicted stem-loop structure was present in the 5' untranslated region of the crayfish ferritin mRNA. C rayfish ferritin does not share the atypical properties of insect ferr itins, such as high molecular mass of intact protein, abundance in hem olymph, and export into vacuoles. We suggest that there are two differ ent types of ferritins distributed in different species: insect-type o r secretory ferritins which are predominant in the snail oocyte and in sects, and vertebrate (crustacean)-type or cytosolic ferritins which a re predominant in vertebrates and crustacea.