EQUILIBRIUM DENATURATION STUDY OF THE MATURE ECTODOMAIN OF THE PROTEIN-TYROSINE PHOSPHATASE IA-2

NOGUERA MARTÍN EZEQUIEL; PRIMO MARÍA EVANGELINA; L.N.F. SOSA; RISSO VALERIA A.; ERMÁCORA MARIO ROBERTO

Congreso; VII IBEROAMERICAN CONGRESS OF BIOPHYSICS 2009; 2009

IA-2 is a protein-tyrosine phosphatase receptor located in secretory vesicles including insulin-secreting granules. Moreover, it is a major autoantigen in type 1 diabetes. This protein undergoes posttranslational modifications, removing the signal peptide and an adjacent fragment (residues 1-448). Mature IA-2 comprises an ectodomain (449-575), a single-pass transmembrane region (576-600), and cytoplasmic domains (601-979). The X ray structure of the mature ectodomain domain (meIA-2) was recently solved in our laboratory. The crystal structure revealed a homodimeric structure, and analytical size exclusion chromatography indicated the existence of a monomer-dimer equilibrium (1). The dimerization process might to play a functional role in mediating interactions with the like molecules of the extracelular matrix and membranes from different cells. To understand the role of noncovalent interactions stabilizing the meIA-2 dimer, the guanidine hydrochloride induced equilibrium denaturation was studied by using far-ultraviolet circular dichroism, intrinsic tyrosine fluorescence and chemical cross-linking as a function of protein concentration. The denaturation transition is reversible, cooperative and the same detected by both spectroscopic probes. Global analysis of the data indicates that the denaturation occurs through a three-state model with a marginally stable intermediate. In conclusion, this finding indicates that the contacts at the surface between the monomers play a fundamental role in the stabilization of the three-dimensional structure of meIA-2.