赖氨酸胍基化对蛋白质组分析的影响

赖氨酸胍基化在蛋白质组学定性和定量研究中起着重要作用，本文系统分析了胍基化前后，HeLa细胞蛋白质经胰蛋白酶酶解产生的3种不同类型肽段的质谱鉴定情况，并探讨了不同肽段质谱响应改变的内在原因。发现赖氨酸在侧链能选择性地发生胍基化反应（其选择性达到96.8%），转化为高精氨酸，碱性增强。因此在正离子质谱模式下，C端为赖氨酸的肽段产生了更多的y离子，提供了许多新的离子碎片信息。在鉴定结果中，此类肽段所占总肽段的比例由原来的51.7%上升为57.3%，并且有1015条新的肽段被检测到。对于不含有赖氨酸的肽段，其鉴定结果在胍基化前后基本没有变化。结果表明，胍基化可以在一定程度上提高质谱鉴定的灵敏度和互补性，提高蛋白质分析的覆盖率。

Effect of the lysine guanidination on proteomic analysis

The guanidination of lysine side chain was paid great attention in recent years. It plays an important role in qualitative and quantitative proteomics. In this study, based on the results of separated peptides extracted from HeLa cells before and after the guanidination by liquid chromatography-tandem mass spectrometry (LC-MS/MS), the effect of the guanidination of three different kinds of peptides was systematically analyzed. It was found that the selectivity of the guanidination of the lysine side chain was as high as 96.8%. The ratio of identified peptides with lysine at C-term to all peptides increased from 51.7% to 57.3% and more new peptides were identified, while the ratio of peptides with lysine in the middle or without lysine changed little. Further study on the ratio of b and y ions indicated that there were more y ions of peptides with lysine at C-term after the guanidination. The results proved that the selective conversion of lysine to homoarginine by the guanidination could increase the sensitivity and selectivity of mass spectrum. The increased basicity and ability to sequester proton of lysine produced more y ions fragmentation information, which contributed to more identified peptides. It concluded that the lysine guanidination can improve the coverage of proteomic analysis.