title: Biophysical characterization of the membrane-proximal ectodomain of the receptor-type protein-tyrosine phosphatase phogrin.
abstract: The receptor-type protein-tyrosine phosphatase (RPTP) phogrin is localized at the membrane of secretory granules of pancreatic islet β-cells and, similarly to the closely related ICA512, plays a role in the regulation of insulin secretion, in ensuring proper granulogenesis and stability, and in the regulation of β-cell growth. The mature membraneproximal ectodomain of phogrin (MPE phogrin) was produced as a recombinant protein and characterized. CD, fluorescence, controlled proteolysis, size-exclusion chromatography, and multi-angle light scattering showed that it is a properlyfolded monomeric domain. Equilibrium experiments, in the presence of guanidinium chloride and thermal unfolding, suggest a two-state mechanism with a ΔG of 2.3-3.3 kcal/mol, respectively. The study establishes common features and differences of MPE phogrin and the homologous ectodomain of ICA512. A homology model of phogrin was built based in the x-ray structure of MPE ICA512. The model is a starting point for modeling the entire receptor and for testing the quaternary structure and interactions of this protein in vivo. A description of the membrane insertion mode and putative interacting surfaces of this large protein is fundamental for the understanding of its biological function.
authors.affiliation: Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Pñna 352, B1876XD Bernal, Buenos Aires, Argentina.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Noguera
authors.forename: Maria E
authors.initials: ME
authors.lastname: Primo
authors.forename: Laura N F
authors.initials: LN
authors.lastname: Sosa
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: D000818:Animals; D002942:Circular Dichroism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8 / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D008565:Membrane Proteins; D011994:Recombinant Proteins; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; C533193:phogrin protein, mouse