title: Beyond bilobal: transferrin homologs having unusual domain architectures.
abstract: BACKGROUND
  Most transferrin family proteins have a familiar bilobal structure, the result of an ancient gene duplication, with an iron binding site in each of two homologous lobes. Scattered throughout the evolutionary tree from algae to mammals, though, are transferrin homologs having other kinds of domain architectures.
  
  
  METHODS
  This review covers a variety of unusual transferrin forms, including monolobals, bilobals with one or both iron-binding sites abrogated, bilobals accessorized with long insertions or with membrane anchors, and even trilobals. The monolobal transferrin homologs from marine invertebrate ascidians are especially highlighted here.
  
  
  CONCLUSIONS
  Unusual transferrin homologs appear scattered through much of the evolutionary tree. For some of these proteins, iron binding and/or iron transport appear to be the primary roles; for others they clearly are not. Many are incompletely or not at all studied.
  
  
  CONCLUSIONS
  Taken together, these proteins begin to offer a glimpse into how the transferrin architecture has been repurposed for a diversity of applications. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
authors: Department of Chemistry, Yale University, USA.
authors: Jean P
authors: JP
authors: Gaffney
authors: Ann M
authors: AM
authors: Valentine
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D005075:Biological Evolution; D006801:Humans; D017136:Ion Transport; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D014168:Transferrin / Q000737:chemistry* / Q000235:genetics; D061250:Transferrins / Q000737:chemistry* / Q000235:genetics
chemical_list: D014168:Transferrin; D061250:Transferrins; D007501:Iron