Under Pressure - Queen, David Bowie & Inorganic Pyrophosphatase

Hyperthermophiles are a type of extremophile that are adapted to live in hot environments above 60⁰C. They are mainly found in the domain Archaea even though some bacteria are able to survive in the high temperatures. Living at such high temperatures requires the need for some specialised proteins that won’t denature when in contact with the extreme heat.

Thermococcus thioreducens is a sulfur reducing archaeon that is a hyperthermophile, but not only does it have the ability to cope with extremely high temperatures, but also to cope with extremely high pressures as it is found in hydrothermal vents along the Mid-Atlantic Ridge. In the paper by Shrestha et al (2015) they take the enzyme inorganic pyrophosphatase (IPPase) and look at the conformational flexibility (the change in the shape of the protein, normally due to environmental factors) and relaxation dynamics (the change in the shape of the protein back to its original form) under different temperatures and pressures. Using quasielastic neutron scattering they compare IPPase to a model protein (hen egg white lysozyme (HEWL)) and analyse the differing times in relaxation dynamics.

They found that IPPase had faster relaxation rates at all temperatures when under pressure which is the opposite of what was observed under ambient pressure. This shows the effects of pressure on protein dynamics and activities.

Whilst the comparison of these two proteins is good as it is comparing the IPPase against a model protein (HEWL), I think its use is limited as the optimal temperature for HEWL is 50⁰C after which it starts to denature, whereas the optimum temperature for IPPase is 85⁰C which is well past the denaturation temperature of HEWL. Because of this I think comparing the relaxation rates of the proteins at say 70⁰C is a bit pointless. It also states in the paper that they are two very different proteins, yet if you know they’re very different should they be compared? I think this paper will have use in the future in fields such as bioengineering where enzymes adapted to high temperatures or pressures will be needed as it provides an understanding of their function under

Shrestha U.R., Bhowmik D., Copley J.R., Tyagi M., Leão J.B. and Chu X.Q.(2015) Effects of pressure on the dynamics of an oligomeric protein from deep-sea hyperthermophile. Proceedings of the National Academy of Sciences. 112(45). pp.13886-13891.