LDL protein nitration: implication for LDL protein unfolding.
Abstract
Oxidatively- or enzymatically-modified low-density lipoprotein (LDL) is intimately involved in the initiation and progression of atherosclerosis. The in vivo modified LDL is electro-negative (LDL(-)) and consists of peroxidized lipid and unfolded apoB-100 protein. This study was aimed at establishing specific protein modifications and conformational changes in LDL(-) assessed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) and circular dichroism analyses, respectively. The functional significance of these chemical modifications and structural changes were validated with binding and uptake experiments to- and by bovine aortic endothelial cells (BAEC). The plasma LDL(-) fraction showed increased nitrotyrosine and lipid peroxide content as well as a greater cysteine oxidation as compared with native- and total-LDL. LC/MS/MS analyses of LDL(-) revealed specific modifications in the apoB-100 moiety, largely involving nitration of tyrosines in the alpha-helical structures and beta(2) sheet as well as cysteine oxidation to cysteic acid in beta(1) sheet. Circular dichroism analyses showed that the alpha-helical content of LDL(-) was substantially lower ( approximately 25%) than that of native LDL ( approximately 90%); conv...Continue Reading
References
Peroxynitrite-mediated alpha-tocopherol oxidation in low-density lipoprotein: a mechanistic approach
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