Expression and physicochemical characterization of an extracellular segment of the receptor protein tyrosine phosphatase IA-2.

PRIMO M.E., SICA M.P., RISSO V.A., POSKUS E., ERMÁCORA M.R.

BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY

Elsevier

Año: 2006 vol. 1764 p. 174 - 181

0167-4838

The receptor protein tyrosine phosphatase superfamily (RPTP) includes proteins with a single transmembrane, one or more intracellular phosphatase, and a variety of extracellular domains. The 106‑kDa insulinoma–associated protein (IA–2, ICA512) receptor is unique among RPTP members because: (a) it has a single, phosphatase‑like intracellular domain identified as one of the most prominent self antigens in autoimmune diabetes; (b) its extracellular region bears no sequence similarity to known domains; (c) it is present in the membrane of secretory granules in neurons and pancreatic b‑cells where it suffers a complex processing; and (d) it has very poorly understood biological properties. In this work, we describe the expression, purification, and physicochemical characterization of residues 449‑576 of IA‑2 (IA‑2ec449‑576). Judging from CD, fluorescence, hydrodynamic, and thermal unfolding analyses, this fragment forms an autonomously folding unit with tight packing and well‑defined secondary and tertiary structure. CD analysis suggests that about 25 % of IA‑2ec449‑576 residues are a‑helical, whereas about the same amount are in b‑sheet structure. The availability of soluble and folded IA‑2ec449‑576 is a step forward toward the characterization of a part of IA‑2 at atomic detail, which may provide new insight in the biology of diabetes, the neurotransmission process, and the dynamic of secretory granules.