Pressure response of protein backbone structure. Pressure‐induced amide ¹⁵N chemical shifts in BPTI

Abstract

The effect of pressure on amide 15 N chemical shifts was studied in uniformly 15 N-labeled basic pancreatic trypsin inhibitor~BPTI! in 90% 1 H 2 O010% 2 H 2 O, pH 4.6, by 1 H-15 N heteronuclear correlation spectroscopy between 1 and 2,000 bar. Most 15 N signals were low field shifted linearly and reversibly with pressure~0.468 6 0.285 ppm02 kbar!, indicating that the entire polypeptide backbone structure is sensitive to pressure. A significant variation of shifts among different amide groups~0-1.5 ppm02 kbar! indicates a heterogeneous response throughout within the three-dimensional structure of the protein. A tendency toward low field shifts is correlated with a decrease in hydrogen bond distance on the order of 0.03 Å02 kbar for the bond between the amide nitrogen atom and the oxygen atom of either carbonyl or water. The variation of 15 N shifts is considered to reflect site-specific changes in f, c angles. For b-sheet residues, a decrease in c angles by 1-2802 kbar is estimated. On average, shifts are larger for helical and loop regions~0.553 6 0.343 and 0.519 6 0.261 ppm02 kbar, respectively! than for b-sheet~0.295 6 0.195 ppm02 kbar!, suggesting that the pressure-induced structural changes~local compressibilities! are larger in helical and loop regions than in b-sheet. Because compressibility is correlated with volume fluctuation, the result is taken to indicate that the volume fluctuation is larger in helical and loop regions than in b-sheet. An important aspect of the volume fluctuation inferred from pressure shifts is that they include motions in slower time ranges~less than milliseconds! in which many biological processes may take place.

Exploring the entire conformational space of proteins by high-pressure NMR

“…The structural changes of comparable magnitude were reported in a crystalline protein at high pressure [10]. The important point here is that up to 2 kbar, the chemical shift changes of almost all 1 H and 15 N nuclei in hen lysozyme and BPTI are linear with pressure [14][15][16][17][19][20][21][22]. This means that linear conformational changes take place with pressure in both secondary and tertiary structures, and hence a linear volume change in Fig.…”

“…Microscopically, compression of a protein volume is accompanied by slight changes in local conformations, which can be studied most sensitively by NMR as chemical shift changes. We found by highpressure NMR in solution that the general compression of the native conformer is accompanied by increased side chain packing [14,15] and shortened hydrogen bond distances on the order of ~0.02 Å on average at 2 kbar [16][17][18][19][20][21], accompanied by slight changes in torsion angles of a few degrees on average in φ, ψ angles [22], all of which occur heterogeneously over the folded protein architecture. The structural changes of comparable magnitude were reported in a crystalline protein at high pressure [10].…”

Species-specific Differences in the Intermediate States of Human and Syrian Hamster Prion Protein Detected by High Pressure NMR Spectroscopy

“…In general, the pressure response of proteins is not isotropic, and the chemical shift changes induced by the local and global conformational changes lead to a nonlinear dependence of the chemical shifts on pressure. The pressure dependence was described by the zero-order coefficient ␦ 0 (p 0 , T 0 ), the first order coefficient B 1 and the second order coefficient B 2 of a Taylor expansion around the pressure p 0 and the temperature T 0 (see Equation 1) (24).…”

Dynamics in the solid-state: perspectives for the investigation of amyloid aggregates, membrane proteins and soluble protein complexes

“…Pressure induced 15 N chemical shift changes Dd P are on the order of 1.5-2.5 ppm GPa -1 . Interestingly, reduced local compressibilities are observed for b-sheets with Dd P,N = 1.5 ppm GPa -1 (Akasaka et al 1999). For 15 N, therefore a distribution of resonances within 3 Hz would be expected.…”