The Phosphoenolpyruvate-Dependent Phosphotransferase System of Staphylococcus aureus. 3. 1H and 31P Nuclear-Magnetic-Resonance Studies on the Phosphocarrier Protein HPr; Tyrosine Titration and Denaturation Studies

作者：W Mäurer, Heinz Rüterjans, Otto Schrecker, Wolfgang Hengstenberg, Martin GASSNER, Dietmar Stehlik · 发表于：European Journal of Biochemistry · 年份：1977 · DOI：10.1111/j.1432-1033.1977.tb11529.x · 被引用次数：19 · 研究领域：Antimicrobial Resistance in Staphylococcus、Bacterial Genetics and Biotechnology、Enzyme Structure and Function

The phosphocarrier protein HPr has been investigated by proton nuclear magnetic resonance (NMR) at 270 MHz in order to evaluate structural properties of the whole molecule and its active site. The titration behaviour of the three tyrosines of the HPr protein was analysed by monitoring the chemical shifts of the aromatic proton resonances of these residues as a function of pH. It was found that the HPr protein contains a lot of slowly exchanging NH backbone protons which suggested a relatively rigid secondary structure of the protein molecule itself although it contains no disulfide bridges. The HPr protein shows a sharp reversible denaturation behaviour at alkaline pH values. Between pH 10.8 and 11.1 two C-2 proton resonance peaks for the single histidine residue could be observed together with abrupt changes in the aromatic and aliphatic absorption region of the HPr protein which are due to chemical exchange processes. The NMR spectrum of the HPr protein is only changed a little upon raising the temperature from 14 degrees C to 70 degrees C. At 76 degrees C all resonances in the spectrum broaden and almost disappear. This process is irreversible.