Abstract
The apolipoprotein (apo) B-100-specific monoclonal
antibody MB47 has been widely used in lipoprotein metabolism
and atherosclerosis research. When bound to apoB-100 on low
density lipoproteins (LDL), antibody MB47 completely blocks
the binding of LDL to the LDL receptor. The epitope for antibody
MB47 has previously been mapped to the vicinity of
apoB-100 amino acid (aa) residue 3500. To map the epitope for
antibody MB47 more precisely, we used recombinant bacterial
fusion proteins. Antibody MB47 bound strongly to a fusion protein
containing apoB-100 aa 3214-3728, but no specific binding
was observed to fusion proteins containing aa 3214-3351,
3214-3506, 3351-3506, or a fusion protein containing aa
3214-3351 and 3506-3728. Although antibody MB47 did not
bind to aa 3214-3506, it did bind to aa 3214-3510. Further fusion
protein studies revealed that antibody MB47 bound to aa
3429-3510, but bound only very weakly to aa 3453-3510, indicating
that aa 3429-3453 constitute an important part of the
MB47 epitope. Subsequent fusion protein studies revealed that
MB47 bound much more strongly to aa 3429-3523, 3429-3544,
3429-3565, and 3429-3590 than to aa 3429-3510. Thus, aa
3507-3523 also constitute an important part of the MB47 epit0pe.
m In summary, the fusion protein data indicated that
two nonlinear domains of apoB-100 separated by - 53 aa (the 25
residues from aa 3429 to 3453 and the 17 residues from aa 3507
to 3523) form key parts of the MB47 epitope. Antibody MB47
failed to bind to any of 15 different synthetic apoB peptides that
spanned aa 3415-3510, a finding that is consistent with the fusion
protein data indicating that the MB47 epitope is formed by
the conformational alignment of discontinuous amino acid sequences.
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