title: Peroxynitrite-induced structural perturbations in human IgG: A physicochemical study.
abstract: IgG is an important defence protein. To exhibit optimum function the molecule must maintain its native structure. Peroxynitrite is a potent oxidizing and nitrating agent produced in vivo under pathophysiological conditions. It can oxidize and/or nitrate various amino acids causing changes in the structure and function of proteins. Such proteins may be involved in the pathogenesis of many inflammatory diseases, including rheumatoid arthritis. In the present work, peroxynitrite-induced structural changes in IgG have been studied by UV-visible, fluorescence, CD, FT-IR, DLS spectroscopy and DSC as well as by SDS-PAGE. Peroxynitrite-modified IgG exhibited hyperchromicity at 280 nm, quenching of tryptophan fluorescence, increase in ANS fluorescence, loss of β-sheet, shift in the positions of amide I and amide II bands, appearance of new peak in FT-IR, attachment of nitro residues and increase in melting temperature, compared to native IgG. Furthermore, peroxynitrite-modified IgG exhibited an additional peak at 420 nm, quenching in tyrosine fluorescence and enhancement in dityrosine fluorescence compared to native IgG. Generation of nitrotyrosine, dityrosine and nitrotryptophan was also observed in peroxynitrite-modified IgG. Gross structural changes in IgG caused by peroxynitrite and observed in vitro may favour autoantibodies induction in vivo under similar conditions.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002, U.P., India.
authors.forename: Mir Yasir
authors.initials: MY
authors.lastname: Arfat
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002, U.P., India.
authors.forename: Zarina
authors.initials: Z
authors.lastname: Arif
authors.affiliation: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202002, U.P., India.
authors.forename: Sumit Kumar
authors.initials: SK
authors.lastname: Chaturvedi
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002, U.P., India.
authors.lastname: Moinuddin
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002, U.P., India. Electronic address: kalam786@rediffmail.com.
authors.forename: Khursheed
authors.initials: K
authors.lastname: Alam
mesh_terms: D001172:Arthritis, Rheumatoid / Q000378:metabolism; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry*; D007249:Inflammation; D008027:Light; D008856:Microscopy, Fluorescence; D010100:Oxygen / Q000737:chemistry; D030421:Peroxynitrous Acid / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012542:Scattering, Radiation; D012685:Sepharose / Q000737:chemistry; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D007074:Immunoglobulin G; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D014364:Tryptophan; D012685:Sepharose; D010100:Oxygen
keywords: Autoantibody; Human IgG; Nitrotyrosine; Peroxynitrite; Protein structure