Laboratory for Pharmaceutical Biotechnology, Ghent University, Ghent, Belgium.
J Proteome Res. 2012 Nov 2;11(11):5245-51. doi: 10.1021/pr3004453. Epub 2012 Oct 11.
Citrullination is a post-translational modification of arginine, resulting in a loss of positive charge and a 1 Da mass increase. Research on citrullinated proteins is crucial in rheumatoid arthritis, an autoimmune disease characterized by the presence of antibodies against citrullinated proteins. However, little is known about the location or quantity of deiminated arginine residues in these proteins. Since citrullination gives rise to a mass gain of only 1 Da, the isotope pattern of the citrullinated and the noncitrullinated version of a peptide will overlap. However, the difference between the theoretical, or noncitrullinated, and the measured isotope pattern can be used to quantify the amount of citrullination. We developed a method to quantify citrullinated peptides by means of their skewed isotopic distribution pattern. The method was first optimized with synthetic peptides, after both direct infusion and RP-HPLC separation on an ESi-QqTOF mass spectrometer. Additionally, we analyzed synovial fluid samples from rheumatoid arthritis patients and were able to quantify citrullinated peptides originating from citrullinated fibrinogen, a well-known antigen.
瓜氨酸化是精氨酸的一种翻译后修饰，导致正电荷丢失和 1 Da 质量增加。瓜氨酸化蛋白的研究对于类风湿关节炎至关重要，类风湿关节炎是一种自身免疫性疾病，其特征是存在针对瓜氨酸化蛋白的抗体。然而，对于这些蛋白中脱氨精氨酸残基的位置或数量知之甚少。由于瓜氨酸化仅导致 1 Da 的质量增加，因此肽的瓜氨酸化和非瓜氨酸化版本的同位素模式会重叠。然而，可以使用理论上的（非瓜氨酸化）和测量的同位素模式之间的差异来定量瓜氨酸化的程度。我们开发了一种通过肽的倾斜同位素分布模式来定量瓜氨酸化肽的方法。该方法首先在 ESi-QqTOF 质谱仪上通过合成肽进行了直接注入和 RP-HPLC 分离的优化。此外，我们分析了来自类风湿关节炎患者的滑液样本，并能够定量源自瓜氨酸化纤维蛋白原的瓜氨酸化肽，瓜氨酸化纤维蛋白原是一种众所周知的抗原。
