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Tautomeric state and pK a of the phosphorylated active site histidine in the N‐terminal domain of enzyme I of the Escherichia coli phosphoenolpyruvate: Sugar phosphotransferase system
Author(s) -
Garrett Daniel S.,
Clore G.Marius,
Gronenborn Angela M.,
Seok YeongJae,
Peterkfsky Alan
Publication year - 1998
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560070329
Subject(s) - pep group translocation , phosphoenolpyruvate carboxykinase , escherichia coli , histidine , biochemistry , chemistry , enzyme , active site , phosphotransferase , phosphorylation , gene
The phosphorylated form of the N‐terminal domain of enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system of Escherichia coli has been investigated by one‐bond and long‐range 1 H ‐ 1.5 N correlation spectroscopy. The active site His 189 is phosphorylated at the Nϵ2 position and has a p K a of 7.3, which is one pH unit higher than that of unphosphorylated His 189. Because the neutral form of unphosphorylated His 189 is in the Nδ1‐H tautomer, and its Nϵ2 atom is solvent inaccessible and accepts a hydrogen bond from the hydroxyl group of Thr 168, both protonation and phosphorylation of His 189 must be accompanied by a change in the side‐chain conformation of His 189, specifically from a X 2 angle in the g + conformer in the unphosphorylated state to the g − conformer in the phosphorylated state.