Biophysical characterization of the membrane-proximal ectodomain of phogrin

NOGUERA, M E; PRIMO, M E; SOSA, L; RISSO, V A; POSKUS, E; ERMÁCORA, M. R.

PROTEIN AND PEPTIDE LETTERS

BENTHAM SCIENCE PUBL LTD

Lugar: Oak Park; Año: 2012

0929-8665

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 membrane-proximal ectodomain of phogrin (MPE phogrin) was produced as a recombinant protein and characterized. CD, fluorescence, controlled proteolysis, and size-exclusion chromatography showed that it is a properly-folded dimeric domain. Equilibrium experiments suggest that the dissociation and unfolding of MPE phogrin are uncoupled events. The study establishes several common features of MPE phogrin and the homologous ectodomain of ICA512. Homology modeling allowed building two dimers which may represent biologically relevant association modes. The proposed dimeric structures are starting points for modeling the entire receptor and test its existence in vivo. A description of the membrane insertion mode, and putative interacting surfaces of this large protein is the fundamental step toward the understanding of its biological function.