Direct Evidence for apo B-100-Mediated Copper Reduction: Studies with Purified apo B-100 and Detection of Tryptophanyl Radicals
Copper binding to apolipoprotein B-100 (apo B-100) and its reduction by endogenous components of low-density lipoprotein (LDL) represent critical steps in copper-mediated LDL oxidation, where cuprous ion (Cu(I)) generated from cupric ion (Cu(II)) reduction is the real trigger for lipid peroxidation....
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Published in | Archives of biochemistry and biophysics Vol. 384; no. 2; pp. 335 - 340 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Elsevier Inc
15.12.2000
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Subjects | |
Online Access | Get full text |
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Summary: | Copper binding to apolipoprotein B-100 (apo B-100) and its reduction by endogenous components of low-density lipoprotein (LDL) represent critical steps in copper-mediated LDL oxidation, where cuprous ion (Cu(I)) generated from cupric ion (Cu(II)) reduction is the real trigger for lipid peroxidation. Although the copper-reducing capacity of the lipid components of LDL has been studied extensively, we developed a model to specifically analyze the potential copper reducing activity of its protein moiety (apo B-100). Apo B-100 was isolated after solubilization and extraction from size exclusion-HPLC purified LDL. We obtained, for the first time, direct evidence for apo B-100-mediated copper reduction in a process that involves protein-derived radical formation. Kinetics of copper reduction by isolated apo B-100 was different from that of LDL, mainly because apo B-100 showed a single phase-exponential kinetic, instead of the already described biphasic kinetics for LDL (namely α-tocopherol-dependent and independent phases). While at early time points, the LDL copper reducing activity was higher due to the presence of α-tocopherol, at longer time points kinetics of copper reduction was similar in both LDL and apo B-100 samples. Electron paramagnetic resonance studies of either LDL or apo B-100 incubated with Cu(II), in the presence of the spin trap 2-methyl-2-nitroso propane (MNP), indicated the formation of protein-tryptophanyl radicals. Our results supports that apo B-100 plays a critical role in copper-dependent LDL oxidation, due to its lipid-independent-copper reductive ability. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0003-9861 1096-0384 |
DOI: | 10.1006/abbi.2000.2102 |