Biophysical characterization of the membrane-proximal ectodomain of the receptor-type protein-tyrosine phosphatase phogrin

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. © 2013 bentham science publishers.