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15N and 1H NMR study of histidine containing protein (HPr) from Staphylococcus carnosus at high pressure

Published online by Cambridge University Press:  01 April 2000

HANS ROBERT KALBITZER
Affiliation:
University of Regensburg, Institute of Biophysics and Physical Biochemistry, Regensburg, Germany
ADRIAN GÖRLER
Affiliation:
University of Regensburg, Institute of Biophysics and Physical Biochemistry, Regensburg, Germany
HUA LI
Affiliation:
Department of Molecular Science, Graduate School of Science and Technology, Kobe University, Kobe, Japan
PETER V. DUBOVSKII
Affiliation:
Department of Molecular Science, Graduate School of Science and Technology, Kobe University, Kobe, Japan Present address: Shemyakin and Ouchinnikov Institute of Bioorganic Chemistry, Moscow, Russia.
WOLFGANG HENGSTENBERG
Affiliation:
Ruhr-University Bochum, Department of Biology, Bochum, Germany
CLAUDIA KOWOLIK
Affiliation:
Ruhr-University Bochum, Department of Biology, Bochum, Germany
HIROAKI YAMADA
Affiliation:
Department of Chemistry, Faculty of Science, Kobe University, Kobe, Japan
KAZUYUKI AKASAKA
Affiliation:
Department of Molecular Science, Graduate School of Science and Technology, Kobe University, Kobe, Japan Department of Chemistry, Faculty of Science, Kobe University, Kobe, Japan
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Abstract

The pressure-induced changes in 15N enriched HPr from Staphylococcus carnosus were investigated by two-dimensional (2D) heteronuclear NMR spectroscopy at pressures ranging from atmospheric pressure up to 200 MPa. The NMR experiments allowed the simultaneous observation of the backbone and side-chain amide protons and nitrogens. Most of the resonances shift downfield with increasing pressure indicating generalized pressure-induced conformational changes. The average pressure-induced shifts for amide protons and nitrogens are 0.285 ppm GPa−1 at 278 K and 2.20 ppm GPa−1, respectively. At 298 K the corresponding values are 0.275 and 2.41 ppm GPa−1. Proton and nitrogen pressure coefficients show a significant but rather small correlation (0.31) if determined for all amide resonances. When restricting the analysis to amide groups in the β-pleated sheet, the correlation between these coefficients is with 0.59 significantly higher. As already described for other proteins, the amide proton pressure coefficients are strongly correlated to the corresponding hydrogen bond distances, and thus are indicators for the pressure-induced changes of the hydrogen bond lengths. The nitrogen shift changes appear to sense other physical phenomena such as changes of the local backbone conformation as well. Interpretation of the pressure-induced shifts in terms of structural changes in the HPr protein suggests the following picture: the four-stranded β-pleated sheet of HPr protein is the least compressible part of the structure showing only small pressure effects. The two long helices a and c show intermediary effects that could be explained by a higher compressibility and a concomitant bending of the helices. The largest pressure coefficients are found in the active center region around His15 and in the regulatory helix b which includes the phosphorylation site Ser46 for the HPr kinase. This suggests that this part of the structure occurs in a number of different structural states whose equilibrium populations are shifted by pressure. In contrast to the surrounding residues of the active center loop that show large pressure effects, Ile14 has a very small proton and nitrogen pressure coefficient. It could represent some kind of anchoring point of the active center loop that holds it in the right place in space, whereas other parts of the loop adapt themselves to changing external conditions.

Type
Research Article
Copyright
© 2000 The Protein Society

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