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. Author manuscript; available in PMC: 2020 Jul 18.
Published in final edited form as: ACS Chem Biol. 2019 Oct 7;14(10):2264–2275. doi: 10.1021/acschembio.9b00610

Figure 2.

Figure 2.

ABL1 preferentially phosphorylates Tyr1 directly adjacent to negatively charged residues specifically in the seventh CTD position. (A) LC-MS trace of singly phosphorylated species in three-repeat wild-type CTD substrate (3xWT) treated with ABL1. Phosphorylation sites were localized using UVPD-MS and are indicated on the chromatogram by repeat number. The GPGSGM amino acid sequences at the N-termini are retained after 3C proteolysis of the 6xHis-GST tags prior to LC-MS/MS analysis. The sites of major and minor phosphorylation are indicated by dark or light blue boxes, respectively. (B,C) Extracted chromatograms of singly phosphorylated species in three-repeat CTD substrates with Ser7Glu mutations (3xS7E Mid and Sp) treated with ABL1. The glutamate mutations in each sequence are shown in red. (D) Extracted chromatograms of singly phosphorylated species in three-repeat CTD substrate with Ser2Glu mutation (3xS2E Mid) treated with ABL1.