title: The major yolk protein in sea urchins is a transferrin-like, iron binding protein.
abstract: The major yolk protein (MYP) in sea urchins has historically been classified as a vitellogenin based on its abundance in the yolk platelets. Curiously, it is found in both sexes of sea urchins where it is presumed to play a physiological role in gametogenesis, embryogenesis, or both. Here we present the primary structure of MYP as predicted from cDNAs of two sea urchins species, Strongylocentrotus purpuratus and Lytechinus variegatus. The sequence from these two species share identity to one another, but bear no resemblance to other known vitellogenins. Instead the sequence shares identity to members of the transferrin superfamily of proteins. In vitro iron binding assays, including both (59)Fe overlay assays of MYP enriched coelomic fluid and immunoprecipitation of native iron-bound MYP from coelomic fluid, support this classification. We suggest that one of MYP's transferrin-like properties is to shuttle iron to developing germ cells.
authors.affiliation: Department of Molecular and Cell Biology and Biochemistry, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA.
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Brooks
authors.forename: Gary M
authors.initials: GM
authors.lastname: Wessel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004527:Egg Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D012617:Sea Urchins; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014168:Transferrin / Q000378:metabolism*; D033863:Transferrin-Binding Proteins
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D004527:Egg Proteins; D033862:Iron-Binding Proteins; D014168:Transferrin; D033863:Transferrin-Binding Proteins; D007501:Iron