A Detailed Map of Oxidative Post-translational Modifications of Human p21ras using Fourier Transform Mass Spectrometry

摘要

P21ras, the translation product of the most commonly mutated oncogene known, is a small guanine nucleotide exchange protein. Oxidant-induced post-translational modifications of p21ras including S-nitrosation and S-glutathiolation have been demonstrated to modulate its activity. Structural characterization of this protein is critical to further understanding the biological functions of p21ras. For peroxynitrite-treated p21ras, five oxidized methionines, five nitrated tyrosines, and at least two oxidized cysteines (including C118) were identified by "bottom-up" analysis with high resolution and high mass accuracy FTMS and the major oxidative modification of C118, Cys~(118)-SO_3H, was confirmed by several tandem mass spectrometry experiments. Additionally, "top-down" analysis was conducted on p21ras S-glutathiolated by oxidized glutathione, and, identified C118 as the major site of glutathiolation among the four surface cysteines.