Structural characterization of the nematode poliprotein subunit ABA-1A from Ascaris suum in the absence of the ligand.

GISELA R. FRANCHINI; MALCOLM W. KENNEDY; BRIAN SMITH; BETINA CÓRSICO

San Javier, Tucumán

Congreso; XLI Annual Meeting of the Argentinean Biophysical Society; 2012

Sociedad Argentina de Biofísica

The polyprotein allergens/antigens of nematodes (NPAs) are small, helix-rich proteins, and have no known structural counterparts in other phyla. The term polyprotein refers to the production of NPAs as large precursors comprising tandemly repeated units that are cleaved posttranslationally into multiple ~15 kDa protein units which may have similar or different functions. The biochemical activity of the NPA of A. suum was first described as a binding protein for small lipids such as fatty acids and retinoids (1). Recently, the structure of a single unit of the polyprotein array has been solved in the presence of saturating concentration of oleic acid describing two binding sites (2). In the present project we are working with ABA-1A in the absence of the ligand (apo form) and its atomic structure is under analysis employing NMR spectroscopy, for which high quality data have already been obtained and full structure calculation is in progress. In order to obtain more information about the structural perturbations due to ligand binding; an oleic acid titration of ABA-1A monitored by NMR spectroscopy was performed. Briefly, it was possible to distinguish two binding events according to the nature of the perturbations observed. The first event occurs principally at the early titration stages and would be compatible with a high affinity binding process while the second event occurs later and would be compatible with a low affinity one.