规模化蛋白质生物质谱鉴定中肽段氨基端环化修饰现象

N-Terminal Cyclization of Peptides in Large-scale Protein Identification Based on Biological Mass Spectrometry

对蛋白质样品制备中引入的氨基酸残基的一种现象——蛋白质酶切肽段氨基端的环化修饰现象的初步研究结果显示,很多以谷氨酰胺(Q)或氨乙酰化修饰的半胱氨酸(CAM_C)残基起始的肽段会发生氨基端的环化修饰,且修饰反应不完全,在同一样本中修饰与非修饰两种状态常同时存在,并且环化修饰后的肽段的反相色谱保留时间发生延迟。在数据库检索时添加环化修饰,可以提高蛋白质的鉴定成功率。本研究结果为大规模的蛋白质质谱数据解析提供了有价值的参考。

Biological mass spectrometry has been developed for the large-scale protein identification. The successful identification of protein in proteomic study is based on an effective match of MS data to the sequence in database. Because of the diversity and heterogeneity of protein modification, the experimental data obtained by mass spectrometry does not match the theoretical value sometimes, which makes about 90 percent or more of the tandem mass spectra not be effectively identified. This has become one of the most important technique issues to be resolved in current proteome research. The N-terminal cyclization of peptides, as one of a variety of modification introduced in sample preparation, has been preliminarily studied in this work. The result showed that N-terminal eyelization occurred at the most of the glutamine （Q） or carbamoylmethyl-cysteine（CAM_C） residues and the reaction is often incomplete or partial, both types of peptides could often exist in .its respective state at the same time, and the behavior of modified peptides in revered phase chromatography is also changed. The success rate of protein identification could be obviously improved if adding the N-terminal cyclization modification in the database searching. These results will be very helpful in the mass spectrometric data analysis of proteomic study.