title: Preservation of biological function despite oxidative modification of the apolipoprotein A-I mimetic peptide 4F.
abstract: Myeloperoxidase (MPO)-derived hypochlorous acid induces changes in HDL function via redox modifications at the level of apolipoprotein A-I (apoA-I). As 4F and apoA-I share structural and functional properties, we tested the hypothesis that 4F acts as a reactive substrate for hypochlorous acid (HOCl). 4F reduced the HOCl-mediated oxidation of the fluorescent substrate APF in a concentration-dependent manner (ED(50) ∼ 56 ± 3 μM). This reaction induced changes in the physical properties of 4F. Addition of HOCl to 4F at molar ratios ranging from 1:1 to 3:1 reduced 4F band intensity on SDS-PAGE gels and was accompanied by the formation of a higher molecular weight species. Chromatographic studies showed a reduction in 4F peak area with increasing HOCl and the formation of new products. Mass spectral analyses of collected fractions revealed oxidation of the sole tryptophan (Trp) residue in 4F. 4F was equally susceptible to oxidation in the lipid-free and lipid-bound states. To determine whether Trp oxidation influenced its apoA-I mimetic properties, we monitored effects of HOCl on 4F-mediated lipid binding and ABCA1-dependent cholesterol efflux. Neither property was altered by HOCl. These results suggest that 4F serves as a reactive substrate for HOCl, an antioxidant response that does not influence the lipid binding and cholesterol effluxing capacities of the peptide.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA. crwhite@uab.edu
authors.forename: C Roger
authors.initials: CR
authors.lastname: White
authors.forename: Geeta
authors.initials: G
authors.lastname: Datta
authors.forename: Amanda K W
authors.initials: AK
authors.lastname: Buck
authors.forename: Manjula
authors.initials: M
authors.lastname: Chaddha
authors.forename: Gautam
authors.initials: G
authors.lastname: Reddy
authors.forename: Landon
authors.initials: L
authors.lastname: Wilson
authors.forename: Mayakonda N
authors.initials: MN
authors.lastname: Palgunachari
authors.forename: Mohammad
authors.initials: M
authors.lastname: Abbasi
authors.forename: G M
authors.initials: GM
authors.lastname: Anantharamaiah
mesh_terms: D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I / Q000737:chemistry*; D001692:Biological Transport / Q000187:drug effects; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D006801:Humans; D006997:Hypochlorous Acid / Q000378:metabolism / Q000494:pharmacology; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction / Q000187:drug effects; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D057786:Peptidomimetics / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D016632:Apolipoprotein A-I; D010455:Peptides; D057786:Peptidomimetics; D006997:Hypochlorous Acid; D002784:Cholesterol