INVESTIGADORES
FALOMIR LOCKHART Lisandro Jorge
congresos y reuniones científicas
Título:
Sterol carrier protein of Yarrowia lipolytica transfers fatty acids to acceptor membranes through a collision-mediated mechanism
Autor/es:
FALOMIR LOCKHART, LISANDRO J.; BURGARDT, NOELIA I; FERREYRA, RAUL G; CEOLIN, MARCELO; ERMÁCORA, MARIO E; CÓRSICO B.
Lugar:
Montevideo, Uruguay
Reunión:
Congreso; 6th International Conference of Biological Physics (ICBP); 2007
Institución organizadora:
IUPAB/SAB
Resumen:
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 from YLSCP2 to 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 donor. Binding of AOFA and relative
partition coefficient for AOFA between YLSCP2 and vesicles were determined in
order to establish the transfer experiments 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 from YLSCP2 to model zwitterionic membranes was examined as a
function of increasing SUV concentration, showing a proportional increase in
transfer rates as a function of vesicle concentration, 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 donor protein and acceptor membranes are involved. AOFA transfer from YLSCP2 was increased from
4-fold to over 30-fold to acceptor membranes which contained an additional 25
mol % negatively charged phosphatidylserine or cardiolipin, respectively. Our
results suggest that YLSCP2 is a membrane interactive protein which is able to
transfer fatty acids to acceptor membranes through a collision-mediated
mechanism which involves electrostatic interactions between protein and
membrane.