Effects of pressure on the dynamics of an oligomeric protein from deep-sea hyperthermophile.
Inorganic pyrophosphatase (IPPase) from Thermococcus thioreducens is a large oligomeric protein derived from a hyperthermophilic microorganism that is found near hydrothermal vents deep under the sea, where the pressure is up to 100 MPa (1 kbar). It has attracted great interest in biophysical research because of its high activity under extreme conditions in the seabed. In this study, we use the quasielastic neutron scattering (QENS) technique to investigate the effects of pressure on the conformational flexibility and relaxation dynamics of IPPase over a wide temperature range. The β-relaxation dynamics of proteins was studied in the time ranges from 2 to 25 ps, and from 100 ps to 2 ns, using two spectrometers. Our results indicate that, under a pressure of 100 MPa, close to that of the native environment deep under the sea, IPPase displays much faster relaxation dynamics than a mesophilic model protein, hen egg white lysozyme (HEWL), at all measured temperatures, opposite to what we observed previously under ambient pressure. This contradictory observation provides evidence that the protein energy landscape is distorted by high pressure, which is significantly different for hyperthermophilic (IPPase) and mesophilic (HEWL) proteins. We further derive from our observations a schematic denaturation phase diagram together with energy landscapes for the two very different proteins, which can be used as a general picture to understand the dynamical properties of thermophilic proteins under pressure.
Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201;
Utsab R
UR
Shrestha
Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201;
Debsindhu
D
Bhowmik
National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, MD 20899;
John R D
JR
Copley
National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, MD 20899; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742.
Madhusudan
M
Tyagi
National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, MD 20899;
Juscelino B
JB
Leão
Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201; chux@wayne.edu.
Xiang-qiang
XQ
Chu
D019843:Archaeal Proteins / Q000737:chemistry*; D001704:Biopolymers / Q000737:chemistry*; D008386:Marine Biology; D011312:Pressure; D019712:Thermococcus / Q000201:enzymology*
D019843:Archaeal Proteins; D001704:Biopolymers
denaturation phase diagram; energy landscape; mode coupling theory; protein dynamics; quasielastic neutron scattering