This paper describes the effect of N-capping substitutions on the structure and stability of
histidine-containing protein (HPr). We have used NMR spectroscopy and conformational
stability studies to quantify changes in local and global free energy due to mutagenesis at
Ser46, the N-cap for helix B in HPr. Previous NMR studies suggested that helix B of
Escherichia coli HPr is dynamic as judged by the rate of exchange of amide protons with
solvent. Ser46 was chosen because it is the site of regulatory phosphorylation in HPrs from …