Extended Data Fig. 9: Liquid chromatography–mass spectrometry (LC–MS) analysis of the products in nucleophile reactivity screening.
From: Genetic code expansion reveals aminoacylated lysine ubiquitination mediated by UBE2W
a, LC–MS analysis of the results of incubation of E2~Ub with AsnK in Supplementary Fig. 11. Freshly purified Ub protein has two MS peaks, Ub (Ubiquitin lacking N terminal Met) and Ub* (acetylated Ub carrying N terminal Met). The desired products are indicated by arrows. And the unwanted products (or the side products) were detected and indicated by triangles in UBE2J2 and UBE2R1. b, LC–MS analysis of the results of incubation of UBE2R1~Ub with AsnK in the presence or absence of ATP. The side products were generated by reaction with ATP instead of AsnK. c, LC–MS analysis of the results of incubation of UBE2W~Ub with the indicated aminoacylated lysine individually or simultaneously. In the figure, the pKa value of AsnK is lower than that of GlnK. And the pKa value of MetK is lower than that of ThrK.
