Ji Yuhuan, Liu Minjing, Bachschmid Markus M, Costello Catherine E, Lin Cheng
Anal Chem. 2015 Jun 2;87(11):5500-4. doi: 10.1021/acs.analchem.5b00249. Epub 2015 May 20.
Bottom-up proteomics is a powerful tool for characterization of protein post-translational modifications (PTMs), where PTMs are identified at the peptide level by mass spectrometry (MS) following protein digestion. However, enzymatic digestion is associated with additional sample processing steps that may potentially introduce artifactual modifications. Here, during an MS study of the PTMs of the regulator of G-protein signaling 4, we discovered that the use of ProteaseMAX, which is an acid-labile surfactant commonly used to improve protein solubilization and digestion efficiency, can lead to in vitro modifications on cysteine residues. These hydrophobic modifications resemble S-palmitoylation and hydroxyfarnesylation, thus discouraging the use of ProteaseMAX in studies of lipid modifications of proteins. Furthermore, since they target the cysteine thiol group, the presence of these artifacts will inevitably lead to inaccuracies in quantitative analysis of cysteine modifications.
自下而上蛋白质组学是表征蛋白质翻译后修饰（PTM）的强大工具，在蛋白质消化后通过质谱（MS）在肽水平鉴定PTM。然而，酶消化与额外的样品处理步骤相关，这些步骤可能会潜在地引入人为修饰。在此，在对G蛋白信号调节因子4的PTM进行质谱研究期间，我们发现使用ProteaseMAX（一种常用于提高蛋白质溶解度和消化效率的酸不稳定表面活性剂）会导致半胱氨酸残基发生体外修饰。这些疏水修饰类似于S-棕榈酰化和羟基法尼基化，因此不鼓励在蛋白质脂质修饰研究中使用ProteaseMAX。此外，由于它们靶向半胱氨酸硫醇基团，这些假象的存在将不可避免地导致半胱氨酸修饰定量分析的不准确。
