Evidence for a Post-Translational Modification, Aspartyl Aldehyde, in a Photosynthetic Membrane Protein

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• 作者：Lorraine B. Anderson ; Anthony J. A. Ouellette ; Julian Eaton-Rye ; Melissa Maderia ; Michael J. MacCoss ; John R. Yates ; III ; and Bridgette A. Barry
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：July 14, 2004
• 年：2004
• 卷：126
• 期：27
• 页码：8399 - 8405
• 全文大小：119K
• 年卷期：v.126,no.27(July 14, 2004)
• ISSN：1520-5126

文摘

In oxygenic photosynthesis, photosystem II (PSII) carries out the oxidation of water and reductionof plastoquinone. Three PSII subunits contain reactive groups that covalently bind amines and phenylhydrazine. It has been proposed that these reactive groups are carbonyl-containing, co- or post-translationallymodified amino acids (Ouellette et al. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 2204 and Anderson et al. J.Biol. Chem. 2000, 275, 4920). To identify modified amino acid residues in one of the PSII subunits (CP47),tandem mass spectrometry was performed. Modified residues were affinity-tagged with either biotin-LC-hydrazide or biocytin hydrazide, which are known to label carbonyl groups. The affinity-tagged subunitwas isolated by denaturing gel electrophoresis, and tryptic peptides were then subjected to affinity purificationand tandem mass spectrometry. This procedure identified a hydrazide-labeled peptide, which has thesequence XKEGR. This result is supported by quantitative results acquired from peptide mapping andmethylamine labeling. The gene sequence and these tandem data predict that the first amino acid, X,which is labeled with the hydrazide reagent, is a modified form of aspartic acid. On the basis of these data,we propose that D348 of the CP47 subunit is post- or co-translationally modified to give a novel aminoacid side chain, aspartyl aldehyde.