A single copy of apolipoprotein B-48 is present on the human chylomicron remnant.
Individuals homozygous for the e2 allele encoding apolipoprotein E exhibit a remnant removal defect and accumulate substantial levels of intestinally derived particles containing apolipoprotein B-48 (apoB-48). Such lipoproteins were isolated from the plasma of E2/E2 individuals, and further purified by affinity chromatography using a polyclonal antibody specific for selective binding and removal of apoB-100-containing lipoproteins. The unbound lipoproteins, termed chylomicron remnants, were particles with average hydrated diameters of 31.2 nm as determined by dynamic light scattering. They contained apoB-48 and ApoE as their only protein components. The number of apoB-48 molecules on each lipoprotein was assessed by counting the number of antibody molecules bound to the surface of the chylomicron remnants, using either a monoclonal antibody specific for a single epitope on apoB-48 or a mixture of two such monoclonal antibodies specific for widely separated epitopes. The results of this analysis seem unambiguous: no more than one apoB-48 resides on the chylomicron remnant. Because apoB appears to be unable to transfer among lipoprotein particles, it may be inferred that nascent chylomicrons also contain a single copy of apoB-48.
Phillips
M L
ML
Department of Chemistry and Biochemistry, University of California-Los Angeles 90095-1569, USA.
Pullinger
C
C
Kroes
I
I
Kroes
J
J
Hardman
D A
DA
Chen
G
G
Curtiss
L K
LK
Gutierrez
M M
MM
Kane
J P
JP
Schumaker
V N
VN
D000911:Antibodies, Monoclonal / Q000032:analysis / Q000276:immunology / Q000302:isolation & purification; D053299:Apolipoprotein B-100; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D002846:Chromatography, Affinity; D002914:Chylomicrons / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis / Q000276:immunology; D006801:Humans; D016253:Microscopy, Immunoelectron; D016622:Silver Staining
D000911:Antibodies, Monoclonal; D053299:Apolipoprotein B-100; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B; D002914:Chylomicrons; D000939:Epitopes