Novel lipid binding proteins from relevant parasitic helminths: structure-function analysis based on biophysical techniques.

MARINA IBAÑEZ SHIMABUKURO; MARÍA FLORENCIA REY; JORGE LUIS PÓRFIDO; VALERIA SILVA; GISELA R. FRANCHINI; MALCOLM W. KENNDY; ALAN COOPER; BRIAN SMITH; BETINA CÓRSICO

La Plata

Conferencia; Humboldt Kollege-International Conference on Physics; 2011

Humboldt Kollege

Parasitic helminths express lipid-binding proteins (LBPs) that are structurally distinct from those of their host. These proteins bind a wide range of lipid classes such as fatty acids, retinoids, eicosanoids, triglycerides, phospholipids and cholesterol. Due to helminth?s limited lipid metabolism, LBP?s have been proposed to participate in parasites development and in the interaction with the host. To understand the mechanisms involved, we have selected four important types of LBPs from highly pathogenic helminth parasites: a) a novel class of fatty acid and retinol binding protein with a structure that has no known counterpart, b) relatives of the fatty acid binding protein family, including members that are structurally modified in ways that are unique to nematodes, c) Antigen B, a member of a new family of ligand binding proteins present in cestodes, and d) nematode polyprotein allergens/antigens. Their atomic structures are under analysis employing NMR spectroscopy, for which we have already obtained high quality data and full structure determination is in progress. Protein-ligand interactions have also been studied by NMR, observing changes in NMR spectra, when stripped and reloaded samples are compared, evidencing conformational changes produced during the binding process. We are also analyzing their ligand-binding parameters (n, K, DH and DS) employing fluorescence-based systems and ITC. The studies confirm these LBPs bind natural ligands and fluorescent analogues in the submicromolar range. Additionally, protein-membrane interaction assays are being performed in vitro in order to characterize LBPs? possible functions. Structural and functional studies will enhance our understanding of the unique features of helminth LBPs that may be related to the survival of the organisms and could be used as potential drug targets.