title: Expression and physicochemical characterization of an extracellular segment of the receptor protein tyrosine phosphatase IA-2.
abstract: The receptor protein tyrosine phosphatase superfamily (RPTP) includes proteins with a single transmembrane, one or more intracellular phosphatase, and a variety of extracellular domains. The 106-kDa insulinoma-associated protein (IA-2, ICA512) receptor is unique among RPTP members because: (a) it has a single, phosphatase-like intracellular domain identified as one of the most prominent self antigens in autoimmune diabetes; (b) its extracellular region bears no sequence similarity to known domains; (c) it is present in the membrane of secretory granules in neurons and pancreatic beta-cells where it suffers a complex processing; and (d) it has very poorly understood biological properties. In this work, we describe the expression, purification, and physicochemical characterization of residues 449-576 of IA-2 (IA-2ec(449-576)). Judging from CD, fluorescence, hydrodynamic, and thermal unfolding analyses, this fragment forms an autonomously folding unit with tight packing and well-defined secondary and tertiary structure. CD analysis suggests that about 25% of IA-2ec(449-576) residues are alpha-helical, whereas about the same amount are in beta-sheet structure. The availability of soluble and folded IA-2ec(449-576) is a step forward toward the characterization of a part of IA-2 at atomic detail, which may provide new insight in the biology of diabetes, the neurotransmission process, and the dynamic of secretory granules.
authors.affiliation: Cátedra de Inmunología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires (UBA) and IDEHU (CONICET-UBA), Argentina.
authors.forename: María E
authors.initials: ME
authors.lastname: Primo
authors.forename: Mauricio P
authors.initials: MP
authors.lastname: Sica
authors.forename: Valeria A
authors.initials: VA
authors.lastname: Risso
authors.forename: Edgardo
authors.initials: E
authors.lastname: Poskus
authors.forename: Mario R
authors.initials: MR
authors.lastname: Ermácora
mesh_terms: D000595:Amino Acid Sequence; D001324:Autoantigens / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
chemical_list: D001324:Autoantigens; D008565:Membrane Proteins; D011994:Recombinant Proteins; C516862:PTPRN protein, human; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8