YLSCP2, a Soluble Lipid Tranfer Protein from Yeast

FALOMIR-LOCKHART, L. J.; BURGARDT, N. I.; FERREYRA, R. G.; CEOLÍN, M. R.; ERMÁCORA, M. R.; CÓRSICO, B.

Montevideo

Congreso; VI International Conference of Biological Physics- ICBP2007, V Southern Cone Biophysics Congress, XXXVI Annual Meeting of the Argentinean Biophysical Society; 2007

International Union of Pure and Applied Physics, International Union for Pure and Applied Biophysics

Sterol carrier protein-2 (SCP2) is an intracellular, small, basic protein domain widely expressed in all living organisms. SCP2 was originally described as a sterol binding protein, but more recently it has been shown to also bind phospholipids, fatty acids, and fatty acyl-coenzyme A. The biological function of SCP2 remains obscure, although it has been extensively studied in mammalian cells. It is hypothesized that SCP2 targets its ligand molecules into compartmentalized intracellular pools. A novel SCP2 from Yarrowia lipolítica (YLSCP2) has been recently cloned and characterized for its optical, hydrodynamic and thermodynamic properties as well as its fatty acid binding capacity. In this work, employing a fluorescence energy transfer assay, we have analyzed the rates and mechanisms of anthroyloxy-fatty acid (AOFA) transfer between YLSCP2 and phospholipids membranes containing NBD-PC (N-(7-nitro-2,1,3-benzoxadiazol-4-yl) egg phosphatidylcholine) as an energy transfer acceptor of the anthroyloxy group. Binding of AOFA and relative partition coefficient for AOFA between YLSCP2 and vesicles were determined in order to establish the transfer experiment?s conditions. The effect of acceptor membrane phospholipid concentration on rates of ligand transfer has been used to distinguish between aqueous diffusion and collision-mediated mechanisms. AOFA transfer between YLSCP2 and model zwitterionic membranes was examined as a function of increasing concentration, showing a proportional increase in transfer rates, thus suggesting a collision mechanism of FA transfer. Changes in the surface charge properties of the acceptor vesicles can also influence ligand transfer rates if electrostatic interactions between the protein and membranes are involved. AOFA transfer between YLSCP2 and acceptor membranes, which contained an additional 25 mol% negatively charged phosphatidylserine or cardiolipin, was increased. Our results suggest that YLSCP2 is a membrane‑interactive protein which is able to exchange fatty acids with membranes through a collision-mediated mechanism which involves electrostatic interactions between protein and membrane. These findings suggest a putative role for YLSCP2 as a lipid carrier between membranous organelles for distinctive metabolic fates.