Kr. Miller et Js. Parks, INFLUENCE OF VESICLE SURFACE-COMPOSITION ON THE INTERFACIAL BINDING OF LECITHIN, CHOLESTEROL ACYLTRANSFERASE AND APOLIPOPROTEIN-A-I, Journal of lipid research, 38(6), 1997, pp. 1094-1102
Interfacial binding affinities and capacities of lecithin:cholesterol
acyltransferase (LCAT) and apolipoprotein A-I (apoA-I) for surfaces of
different phosphatidylcholine (PC) composition, cholesterol content,
and apolipoprotein content were measured with a vesicle model system.
Native polyacrylamide gel electrophoresis was used to separate Dee pro
tein from vesicle-bound protein. ApoA-I was isolated from human plasma
and radiolabelled with iodine, whereas radiolabelled LCAT was purifie
d from the media of Chinese hamster ovary cells that were transfected
with human LCAT cDNA and incubated in the presence of [S-35] cysteine
and methionine. Bound and free radiolabelled LCAT and apoA-I and cre q
uantified by phosphorimage analysis. ApoA-I binding was not influenced
by cholesterol content (14 mole%) but was influenced by the PC fatty
acyl composition of the vesicle, PC species containing long chain, pol
yunsaturated fatty acids (PUFA) in the sn-2 position resulted in incre
ased binding af finity (K-d = 75-177 nM) but reduced capacity (0.1-0.3
apoA-I/1000 PC) in comparison to sn-1 palmitoyl, sn-2 oleoyl PC (POPC
, 750 nM and 1.4 apoA-I/1000 PC). LCAT binding affinity to POPC (2190
nM) was stronger in die presence of cholesterol (530 nM), and LCAT bin
ding capacity was reduced (2.63 and 0.6 molecules LCAT/1000 PC, respec
tively). In comparison to POPC, LCAT binding affinity to sn-1 palmitoy
l, sn-2 arachidonyl PC was stronger (611 nM) and binding capacity was
reduced (0.7 LCAT/1000 PC). LCAT binding affinity and capacity to sn-1
palmitoyl, sn-2 eicosapentaneoyl PC (2041 nM, and 2.5 LCAT/1000 PC) w
ere similar to those observed for POPC. We conclude that vesicle surfa
ce PC fatty acyl composition and cholesterol content significantly inf
luence LCAT and apoA-I interfacial binding and therefore may alter LCA
T enzymatic activity.