Radiolytic Modification of Acidic Amino Acid Residues in Peptides: Probes for Examining Protein-Protein Interactions

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• 作者：Guozhong Xu and Mark R. Chance
• 刊名：Analytical Chemistry
• 出版年：2004
• 出版时间：March 1, 2004
• 年：2004
• 卷：76
• 期：5
• 页码：1213 - 1221
• 全文大小：184K
• 年卷期：v.76,no.5(March 1, 2004)
• ISSN：1520-6882

文摘

Hydroxyl radical-mediated footprinting coupled with massspectroscopic analysis is a new technique for mappingprotein surfaces, identifying structural changes modulatedby protein-ligand binding, and mapping protein-ligandinterfaces in solution. In this study, we examine theradiolytic oxidation of aspartic and glutamic acid residuesto probe their potential use as structural probes infootprinting experiments. Model peptides containing Aspor Glu were irradiated using white light from a synchrotron X-ray source or a cesium-137 -ray source. Theradiolysis products were characterized by electrospraymass spectrometry including tandem mass spectrometry.Both Asp and Glu are susceptible to radiolytic oxidizationby -rays or synchrotron X-rays. Radiolysis results primarily in the oxidative decarboxylation of the side chaincarboxyl group and formation of an aldehyde group at thecarbon next to the original carboxyl group, giving rise toa characteristic product with a -30 Da mass change. Asimilar oxidative decarboxylation also takes place foramino acids with C-terminal carboxyl groups. The methylene groups in the Asp and Glu side chains also undergooxygen addition forming ketone or alcohol groups withmass changes of +14 and +16 Da, respectively. Characterizing the oxidation reactions of these two acidic residues extends the number of useful side chain probes forhydroxyl radical-mediated protein footprinting from 10(Cys, Met, Trp, Tyr, Phe, Arg, Leu, Pro, His, Lys) to 12amino acid residues, thus enhancing our ability to mapprotein surface structure and in combination with previously identified basic amino acid probes can be used toexamine molecular details of protein-protein interactionsthat are driven by electrostatics.