2 results
15N and 1H NMR study of histidine containing protein (HPr) from Staphylococcus carnosus at high pressure
- HANS ROBERT KALBITZER, ADRIAN GÖRLER, HUA LI, PETER V. DUBOVSKII, WOLFGANG HENGSTENBERG, CLAUDIA KOWOLIK, HIROAKI YAMADA, KAZUYUKI AKASAKA
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- Journal:
- Protein Science / Volume 9 / Issue 4 / April 2000
- Published online by Cambridge University Press:
- 01 April 2000, pp. 693-703
- Print publication:
- April 2000
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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.
Structure of an analog of fusion peptide from hemagglutinin
- PETER V. DUBOVSKII, HUA LI, SHO TAKAHASHI, ALEXANDER S. ARSENIEV, KAZUYUKI AKASAKA
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- Journal:
- Protein Science / Volume 9 / Issue 4 / April 2000
- Published online by Cambridge University Press:
- 01 April 2000, pp. 786-798
- Print publication:
- April 2000
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- Article
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A 20-residue peptide E5 containing five glutamates, an analog of the fusion peptide of influenza virus hemagglutinin (HA) exhibiting fusion activity at acidic pH lower than 6.0–6.5 was studied by circular dichroism (CD), Fourier transform infrared, and 1H-NMR spectroscopy in water, water/trifluoroethanol (TFE) mixtures, dodecylphosphocholine (DPC) micelles, and phospholipid vesicles. E5 became structurally ordered at pH ≤6 and the helical content in the peptide increased in the row: water < water/TFE < DPC ∼ phospholipid vesicle while the amount of β-structure was approximately reverse. 1H-NMR data and line-broadening effect of 5-, 16-doxylstearates on proton resonances of DPC bound peptide showed E5 forms amphiphilic α-helix in residues 2–18, which is flexible in 11–18 part. The analysis of the proton chemical shifts of DPC bound and CD intensity at 220 nm of phospholipid bound E5 showed that the pH dependence of helical content is characterized by the same pKa ≈5.6. Only Glu11 and Glu15 in DPC bound peptide showed such elevated pKas, presumably due to transient hydrogen bond(s) Glu11 (Glu15) δCOO−(H+) … HN Glu15 that dispose(s) the side chain of Glu11 (Glu15) residue(s) close to the micelle/water interface. These glutamates are present in the HA-fusion peptide and the experimental half-maximal pH of fusion for HA and E5 peptides is ∼5.6. Therefore, a specific anchorage of these peptides onto membrane necessary for fusion is likely driven by the protonation of the carboxylate group of Glu11 (Glu15) residue(s) participating in transient hydrogen bond(s).
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