tailieunhanh - Báo cáo khoa học: Re-evaluation of intramolecular long-range electron transfer between tyrosine and tryptophan in lysozymes Evidence for the participation of other residues

One-electron oxidation of six different c-type lysozymes from hen egg white, turkey egg white, human milk, horse milk, camel stomach and tortoise was studied by gamma-and the first step, one tryptophan side chain is oxidized to indolyl free radical, which is produced shown already, the indolyl radical subse-quently oxidizes a tyrosine side chain to the phenoxy radical in an intramolecular this reaction is not total and its stoichiometry depends on the constants also vary between proteins, from 120Æs )1 to 1000Æs )1 at pH and room temperature [extremes are hen and turkey egg white (120Æs )1 ) and human milk (1000Æs )1 )] | Eur. J. Biochem. 270 3565-3571 2003 FEBS 2003 doi Re-evaluation of intramolecular long-range electron transfer between tyrosine and tryptophan in lysozymes Evidence for the participation of other residues Marilvne Stuart-Audette1. Yves Blouauit2 Moshe Faraaai3. Cecile Sicard-Roselli1. Chantal Houee-Levin1 B M V BB F F BB B B w BB w B BF BB BB BB B B BF B B B BB BB BB BB I F B BBB B BB B B BF BB B B B BBB B BB B B BB B B B BF BB BB BB BB w B B B and Pierre Jolles4 1LCP Centre Universitaire Orsay Cedex France 2Institut Curie-Section de Recherche Centre Universitaire Orsay Cedex France 3Department of Nuclear Engineering Ben Gurion University of the Negev Israel 4Laboratoire de Chimie Museum National d Histoire Naturelle and LNCP Universite Paris 6 France One-electron oxidation of six different c-type lysozymes from hen egg white turkey egg white human milk horse milk camel stomach and tortoise was studied by gamma-and pulse-radiolysis. In the fistt tfep one tryptophan iide chain is oxidized to indolyl free radical which is produced quantitatively. As shown ar eridy the indolyl radical uubte-quently oxidizes a tyrosine side chain to the phenoxy radical in an intramolecular reaction. However thss feaciion is not total and its stoichiometry depends on the protein. Rare constants also vary between proteins from 120-s 1 to 1000-s 1 at pH and room temperature extremes are hen and turkey egg white 120-s-1 and human milk 1000-s 1 . In hen and turkey egg white lysozymes we show that another reactive site is the Asn103-Gly104 peptidic bond which gets broken radiolytically. Tpv tik dígetiíon fohowed by HPLC separation and identihcation of the peptides was performed for nonieeadiated and irradiated hen lysozyme. Fluorescence spectra of the peptides indicate that Trp108 and or 111 remain oxidized and that Tyr20 and 53 give bityrosine. Tyr23 appears not to be involved in the process. Thuss new features of long-range intramolecular electron .