EVIDENCE FOR A POST-TRANSLATIONAL MODIFICATION, ASPARTYL ALDEHYDE

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目及 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 在光合作用中，光系统II（PSII）进行水的氧化和质体醌的还原。三个PSII亚基含有共价结合胺和苯肼的反应基团。已经提出这些反应性基团是含羰基的、共修饰或后修饰的氨基酸（Ouellette等人，Proc.Natl. Acad. Sci. U.S.A. 1998，95，2204和安德森等人J. Biol. Chem. 2000，275，4920）。为了鉴定PSII亚基之一（CP 47）中的修饰的氨基酸残基，进行串联质谱。用已知标记羰基的生物素-LC-酰肼或生物胞素酰肼亲和标记修饰的残基。通过变性凝胶电泳分离亲和标记的亚基，然后对胰蛋白酶肽进行亲和纯化和串联质谱。该程序鉴定了具有序列XKEGR的酰肼标记的肽。这一结果得到了肽图谱和甲胺标记定量结果的支持。基因序列和这些串联数据预测，用酰肼试剂标记的第一个氨基酸X是天冬氨酸的修饰形式。在这些数据的基础上，我们提出，D348的CP 47亚基后或共修饰，得到一个新的氨基酸侧链，丙醛。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In oxygenic photosynthesis, photosystem II (PSII) carries out the oxidation of water and reduction of 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-translationally modified 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 subunit was isolated by denaturing gel electrophoresis, and tryptic peptides were then subjected to affinity purification and tandem mass spectrometry. This procedure identified a hydrazide-labeled peptide, which has the sequence XKEGR. This result is supported by quantitative results acquired from peptide mapping and methylamine 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 amino acid side chain, aspartyl aldehyde.