Immunoreactivity and conformation of the P-P-G-M-R-P-P repetitive epitope of the Sm autoantigen (Journal article)

Tsikaris, V./ Vlachoyiannopoulos, P. G./ Panou-Pomonis, E./ Marraud, M./ Sakarellos, C./ Moutsopoulos, H. M./ Sakarellos-Daitsiotis, M.

Anti-Sm antibodies are usually considered highly specific for systemic lupus erythematosus (SLE), while anti-U1 RNP antibodies are found in high titers in patients with mixed connective tissue disease (MCTD). The sequence P-1-P-G-M-R-P-P-7, present in three copies in the Sm (U1-U6 RNA-protein complex) autoantigen, is an important functional domain of the antigenic determinants. The immunoreactivity of this proline-rich repetitive epitope was investigated by testing sera with various autoantibody specificities for reactivity against this epitope, as well as its conformational properties by means of 1D and 2D (1)HNMR spectroscopy. It was found that the P-P-G-M-R-P-P epitope is recognized mainly by anti-U1RNP and/or anti-Sm positive sera, but also by anti-Ro(SSA) (hY1RNA-protein complex) and anti-La(SSB) (hY1RNA-protein complex) positive sera, although these sera are negative for anti-U1RNP and anti-Sm. Conformational analysis of the proline-rich epitope in DMSO-d(6) solution obtained from lyophilized aqueous solution at pH 5 showed the presence of at least three conformers. The main conformer A (62%) is stabilized by an ionic interaction between the guanidinium and the C-terminal carboxylate groups, and the Pro(6)-Pro(7) peptide bond adopts the cis form. A type II beta-turn is also present in the N-terminal sequence (Pro(1)-Pro-Gly-Met(4)-) of this conformer. Conformer B (21%) is also stabilized by a similar ionic interaction, as in conformer A, while the NMR data indicate the absence of a folded structure in the N-terminal tetrapeptide of this conformer. Conformer C (17%) adopts a completely extended structure. The multiple conformers of the P-P-G-M-R-P-P may offer some explanation for the reactivity of sera with various autoantibody specificities against this epitope. (C) Munksgaard 1996.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: immunoreactive peptides,peptide conformation, proline-rich peptides,sm autoantigen,systemic lupus-erythematosus,connective-tissue disease,molecular-dynamics,dimethyl-sulfoxide,residual water,antibodies,antigens,nmr,autoimmunity,peptide
URI: https://olympias.lib.uoi.gr/jspui/handle/123456789/8161
ISSN: 0367-8377
Link: <Go to ISI>://A1996VR18100003
http://onlinelibrary.wiley.com/store/10.1111/j.1399-3011.1996.tb00848.x/asset/j.1399-3011.1996.tb00848.x.pdf?v=1&t=h0e0v5dv&s=3e75c9b5ba7caa475a63a84e79912cacdbdb82fe
Publisher: Munksgaard Int Publ Ltd.
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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