Our long-term goal is to understand how microbes are able to withstand remarkable extremes of temperature, pressure, and chemical composition (P-T-X), by determining how the macromolecular structures comprising the microbes are preserved. Our focus is on the effects of high pressure, which are much less understood than those of temperature. Since high-pressure methods are increasingly being used for food preservation, understanding the effects of pressure is important for human health and welfare. Disturbingly, some mesophilic microbes appear to able to withstand ~10 kbar pressures, while piezophilic (pressure-loving) microbes have been found at maximum pressures of ~1.1 kbar. Determining what pressures will disrupt structures of proteins in cell-like conditions will help to define the limiting pressures that microbes can grow at. Our goal for the proposed work is to understand the interplay of P-T effects on proteins by examining enzymes from psychrophiles (cold-loving) and thermophiles (hot-loving) that are also piezophilic at different P-T. Based on our previous work on a piezophilic psychrophile enzyme, microbes may be mainly adapted for temperature rather than high pressure and enzymes from psychrophiles appear much more fragile than those from thermophiles. The proposed studies will expand the range of growth temperatures of the source organisms to piezophilic thermophile enzymes. They will also address the effects of piezolytes, which are osmolytes that protect against pressure effects, on proteins. Our approach uses molecular dynamics computer simulations and biophysical experiments.
Our specific aims are to:
Aim 1. Understand piezophilicity in other psychrophile enzymes.
Aim 2. Understand piezophilicity in thermophile enzymes.
Aim 3. Understand how piezolytes change pressure effects on proteins.

Public Health Relevance

Computational studies of proteins under pressure will provide a fundamental, molecular understanding of protective mechanisms used by microbes to protect their proteins against high pressure. These mechanisms include genetic modifications of proteins for stability as well as changes in the intracellular milieu. Understanding the nature of these mechanisms is crucial in designing protocols for food preservation that involve high pressure.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Macromolecular Structure and Function D Study Section (MSFD)
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Lyster, Peter
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Georgetown University
Schools of Arts and Sciences
United States
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Huang, Qi; Rodgers, Jocelyn M; Hemley, Russell J et al. (2018) Quasiharmonic Analysis of the Energy Landscapes of Dihydrofolate Reductase from Piezophiles and Mesophiles. J Phys Chem B 122:5527-5533
Teng, Xiaojing; Huang, Qi; Dharmawardhana, Chamila Chathuranga et al. (2018) Diffusion of aqueous solutions of ionic, zwitterionic, and polar solutes. J Chem Phys 148:222827
Ichiye, Toshiko (2018) Enzymes from piezophiles. Semin Cell Dev Biol 84:138-146
Huang, Qi; Rodgers, Jocelyn M; Hemley, Russell J et al. (2017) Extreme biophysics: Enzymes under pressure. J Comput Chem 38:1174-1182
Rodgers, Jocelyn M; Hemley, Russell J; Ichiye, Toshiko (2017) Quasiharmonic analysis of protein energy landscapes from pressure-temperature molecular dynamics simulations. J Chem Phys 147:125103