Localization of apolipoprotein A-I epitopes involved in the activation of lecithin:cholesterol acyltransferase.
Eight murine monoclonal antibodies (Mab) to apolipoprotein A-I were characterized for their epitopes and for their ability to interfere with lecithin:cholesterol acyltransferase (LCAT) activation mediated by apo apoA-I using a synthetic substrate. Using overlapping synthetic peptides we have identified six continuous epitopes that span amino acids 1-10 (Mab A-I-19), 96-101 (Mab A-I-15), 133-141 (Mab A-I-5), 140-145 (Mab A-I-9), 144-148 (Mab A-I-8), and 167-174 (Mab A-I-57). Furthermore, antibodies A-I-11 and A-I-16 recognized discontinuous epitopes, namely amino acids 124-128 and 144-148. When antibodies were tested for their ability to inhibit LCAT activation, an inhibitory effect was observed with those whose epitopes covered the area of apoA-I encompassing amino acids 96-174. From these data we conclude that several areas of apoA-I spanning the middle region of the apolipoprotein act in concert to stimulate LCAT activity, possibly by cooperative interaction with the enzyme.
Uboldi
P
P
Institute of Pharmacological Sciences, University of Milano, Italy.
Spoladore
M
M
Fantappiè
S
S
Marcovina
S
S
Catapano
A L
AL
D000818:Animals; D016632:Apolipoprotein A-I / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites / Q000276:immunology; D004789:Enzyme Activation / Q000276:immunology; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000378:metabolism*
D016632:Apolipoprotein A-I; D000939:Epitopes; D007862:Phosphatidylcholine-Sterol O-Acyltransferase