Effects of pressure on the dynamics of an oligomeric protein from deep-sea hyperthermophile
Effects of pressure on the dynamics of an oligomeric protein from deep-sea hyperthermophile
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DOI：
10.1073/pnas.1514478112
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发表时间：
2015-11-10
影响因子：
11.1
通讯作者：
Chu, Xiang-qiang
中科院分区：
文献类型：
--
作者：
Shrestha, Utsab R.;Bhowmik, Debsindhu;Chu, Xiang-qiang
硫代还原热球菌的无机焦磷酸酶(IPPase)是一种来源于高温微生物的大分子低聚体蛋白，发现于深海热液喷口附近，压力可达100兆帕(1kbar)。由于其在海底极端条件下的高活性，引起了生物物理研究的极大兴趣。在这项研究中，我们使用准弹性中子散射(QENS)技术研究了压力对IPPase在较宽温度范围内构象柔性和松弛动力学的影响。用两台光谱仪分别在2~25ps和100ps~2 ns的时间范围内研究了蛋白质的β松弛动力学。我们的结果表明，在100兆帕的压力下，接近海底自然环境的IPPase在所有测量的温度下都表现出比中温模型蛋白--蛋清溶菌酶(HEWL)更快的松弛动力学，与我们以前在常压下观察到的相反。这一相互矛盾的观察提供了蛋白质能量图谱被高压扭曲的证据，这对于超高温(IPPase)和中温(HEWL)蛋白质来说是显著不同的。我们进一步从我们的观察中得到了一个示意性变性相图以及这两个非常不同的蛋白质的能量图，这可以作为一个概貌来理解高温蛋白质在压力下的动力学性质。
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 beta-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.