STRUCTURE-FUNCTION RELATIONSHIP OF STEROL CARRIER PROTEIN FROM THE YEAST YARROWIA LIPOLYTICA (YLSCP2)

NOELIA I. BURGARDT; FEDERICO J. PEREZ DE BERTI; RAÚL G. FERREYRA; BETINA CORSICOC; MARIO R. ERMÁCORA; MARCELO R. CEOLÍN

Ciudad Autónoma de Buenos Aires

Jornada; Herramientas modernas para el estudio de aspectos estructurales de proteínas; 2009

Academia Nacional de Farmacia y Bioquímica

Intracellular lipid transport is a challenge to cells since lipid molecules have poor aqueous solubility and tend to form micelles. Soluble lipid binding proteins (SLBPs) are one of the cell approaches to alleviate the problem of intracellular trafficking of lipids. Sterol carrier proteins (SCP2) are the only SLBPs found in all the biological kingdoms. SCP2 has a highly conserved structure, binds a broad spectrum of ligands, (including fatty acids, fatty acyl-CoA, acidic phospholipids, cholesterol, etc), and it is distributed in a variety of tissues and subcellular locations. The conformational plasticity of the binding site of SCP2 seems to be related to the binding mechanism, which is still unclear. Several years ago our lab observed that the yeast Yarrowia lipolytica grows in a medium with sodium palmitate as the sole source of carbon and energy. A small lipid binding protein was found in yeast cells extract and was identified as a sterol carrier protein (YLSCP2). Preliminary studies of the recombinant YLSCP2 established that it has well-defined secondary and tertiary structure and binds different ligands with high specificity [1]. The aim of the present work was to get insight on the relationship between structure and function of YLSCP2. To achieve this goal we studied the effect of ligand binding on the structure and stability of the protein, monitored by circular dichroism (CD), small angle X-ray scattering (SAXS) and thermal unfolding. The ligands used were palmitic acid, cis-parinaric acid (AP), palmitoyl-CoA (pCoA), 1,8-anilinonaphthalene sulfonic acid (ANS), dipalmitoyl-glycerol (DPG), egg phosphatidyl choline (EPC), and cholesterol. The results suggest that each ligand produce a differential effect on YLSCP2 conformation and stability and may be useful to uncover the different binding mechanisms.