Histidine phosphorylation in proteins : a characterization of phosphohistidines in the bacterial transcription factor GlcT of Bacillus subtilis Histidin Phosphor 31 NMR Spektroskopie Antiterminator Proteine Phosphotransferasesystem Phosphorylierung Histidinphosphorylierung histidine 31P NMR antiterminator protein phosphotransferase system phosphorylation The present work provides new insight concerning histidine phosphorylation in proteins which is an essential regulatory posttranslational modifi cation. To study histidine phosphorylation a newly developed NMR approach the HNP experiment is presented in this thesis. The HNP experiment provides speci c experimental evidence of phosphorylated histidines in proteins. It allows for the determination of the regiochemistry of phosphohistidines on the basis of three individual peak patterns for distinguishing all three phosphohistidines i.e. 1 and 3 phosphohistidine and 1 3 diphosphohistidine. This novel NMR approach allows the investigation of histidine phosphorylation in proteins under physiological conditions without resorting to chemical shift comparisons reference compounds or radioactively labelled phosphate. In this thesis histidine phosphorylation in the regulatory domains PRDI and PRDII of the Bacillus subtilis antiterminator protein GlcT was intensely studied. GlcT is a transcription factor which regulates the phosphotransferase system (PTS) by modulating the expression level of PTS enzymes (Enzyme I HPr Enzyme II) on a transcriptional level. Upon the phosphorylation of conserved histidines in PRDI and PRDII the function of GlcT is regulated through its aggregation state. In this thesis it is shown that histidines in both PRDs are primarily phosphorylated at their N(Epsilon 2) forming 3 phosphohistidine. In addition we found by ...