Pressure-dependent 13C chemical shifts in proteins: origins and applications.
Pressure-dependent (13)C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure-independent compressibilities. CH(3), CH(2) and CH carbon shifts change on average by +0.23, -0.09 and -0.18 ppm, respectively, due to a combination of bond shortening and changes in bond angles, the latter matching one explanation for the gamma-gauche effect. In addition, there is a residue-specific component, arising from both local compression and conformational change. To assess the relative magnitudes of these effects, residue-specific shift changes for protein G were converted into structural restraints and used to calculate the change in structure with pressure, using a genetic algorithm to convert shift changes into dihedral angle restraints. The results demonstrate that residual (13)C alpha shifts are dominated by dihedral angle changes and can be used to calculate structural change, whereas (13)C beta shifts retain significant dependence on local compression, making them less useful as structural restraints.
Wilton
David J
DJ
Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
Kitahara
Ryo
R
Akasaka
Kazuyuki
K
Williamson
Mike P
MP
D000465:Algorithms; D001426:Bacterial Proteins / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011312:Pressure; D011487:Protein Conformation; D012260:Ribonucleases / Q000737:chemistry; D013210:Staphylococcus
D001426:Bacterial Proteins; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012260:Ribonucleases; C019760:Bacillus amyloliquefaciens ribonuclease