Figure 2.

ComG phosphorylates corramycin in an unprecedented position. (A) HR-LCMS analysis of an in vitro reaction of corramycin with ComG and ATP/MgCl₂. Extracted ion chromatograms (EIC) show a characteristic mass shift of +80 Da, hinting at the addition of a phosphate group (left panel: + ATP/– ComG; right panel: + ComG/ATP). The negative control depicting the reaction of corramycin with ComG, but without ATP, can be found in Figure S3. (B) Tandem MS/MS analysis of the product of the ComG reaction Cor-P (phosphorylated corramycin). Characteristic shifts of y8 and b3 ions highlight the position of phosphorylation being the β-alanine moiety. Full mass tables of corramycin and Cor-P fragmentation by MS/MS analysis are shown in Tables S2 and S3. NMR data of Cor-P can be found in Figure S7.