Fig. 5.

MS/MS spectrum of serine-phosphorylated peptide from phosphomannomutase/phosphoglucomutase ManB (MPN066). The peptide was measured on line by ESI-mass spectrometry using a nanoACQUITY UPLC system coupled to an LTQ Orbitrap mass spectrometer (see “Experimental Procedures”). The phosphorylation site (Ser-149) is located in the conserved phosphoserine signature of phosphosugar mutases. Detection of the same phosphorylated peptide in all 10 spots of ManB (enhanced image section) suggests further post-translational modifications that affect the isoelectric point of the ManB protein.