Biophysical Characterization of Human Receptor-Type Protein Tyrosine Phosphatase ICA512 Ectodomain Expressed in Pichia pastoris

SAMUS, S. IVÁN; FERREYRA, RAUL G.; ERMÁCORA, MARIO. R.

Sierra de la Ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

Human Receptor-Type Protein-Tyrosine Phosphatase ICA512 (or IA-2) is a transmembrane protein located in secretory granules of neuroendocrine cells. Identified as one of the main antigens of autoimmune diabetes, it is associated with protein secretion processes [1]. During insulin secretion, the cytoplasmic domain of ICA512 is cleaved and relocated to the nucleus, where it stimulates the transcription of the insulin gene. The structures of the intracellular pseudocatalytic and extracellular mature domains are known, but the transmembrane domain and several other parts of the receptor are poorly characterized. We recently solved the structure of the mature ectodomain ME ICA512 (residues 449 to 575) and identified potential dimerization interfaces involved in the regulation of the secretion [2,3]. ICA512 is a glycosylated protein and molecular modeling studies suggest that the positioning of the sugar residues imposes steric restraints on the type of dimerization interface. To address this question, we previously expressed ME ICA512 in Pichia pastoris, and the protein secreted to the culture medium was partially purified and biochemically characterized. Now, we further characterized ME ICA512 by CD and fluorescence spectroscopy, to reveal structural features. The implications of these findings for the biological activity of the protein will be discussed. References [1]Hermel et al. Eur J Neurosci. 1999. 8:2609. [2]Primo et al. J Biol Chem. 2008. 283:4674. [3]Primo et al. PLoS ONE. 2011. 6:e24191