Mass Defect Labeling of Cysteine for Improving Peptide Assignment in Shotgun Proteomic Analyses
作者:Hilda Hernandez、Sarah Niehauser、Stacey A. Boltz、Vijay Gawandi、Robert S. Phillips、I. Jonathan Amster
DOI:10.1021/ac0600407
日期:2006.5.1
A method for improving the identification of peptides in a shotgun proteome analysis using accurate mass measurement has been developed. The improvement is based upon the derivatization of cysteine residues with a novel reagent, 2,4-dibromo-(2‘-iodo)acetanilide. The derivitization changes the mass defect of cysteine-containing proteolytic peptides in a manner that increases their identification specificity. Peptide masses were measured using matrix-assisted laser desorption/ionization Fourier transform ion cyclotron mass spectrometry. Reactions with protein standards show that the derivatization of cysteine is rapid and quantitative, and the data suggest that the derivatized peptides are more easily ionized or detected than unlabeled cysteine-containing peptides. The reagent was tested on a 15N-metabolically labeled proteome from M. maripaludis. Proteins were identified by their accurate mass values and from their nitrogen stoichiometry. A total of 47% of the labeled peptides are identified versus 27% for the unlabeled peptides. This procedure permits the identification of proteins from the M. maripaludis proteome that are not usually observed by the standard protocol and shows that better protein coverage is obtained with this methodology.
一种用于改善质谱枪法蛋白质组分析中肽段识别的方法已被开发。该改进基于用一种新型试剂2,4-二溴-(2‘-碘)乙酰苯胺对半胱氨酸残基进行衍生化。衍生化改变了含半胱氨酸的蛋白酶肽的质量缺陷,从而提高了它们的识别特异性。使用基质辅助激光解吸/电离傅里叶变换离子回旋质谱法测量肽段的质量。与蛋白质标准物进行的反应表明,半胱氨酸的衍生化是快速且定量的,数据表明衍生化的肽段比未标记的含半胱氨酸肽段更易于电离或检测。该试剂在M. maripaludis的15N代谢标记蛋白质组上进行了测试。通过其准确的质量值和氮的化学计量比识别蛋白质。共识别到47%的标记肽段,而未标记肽段为27%。该程序允许识别通常在标准协议下无法观察到的M. maripaludis蛋白质,并且表明此方法能够获得更好的蛋白质覆盖率。