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The chaperonin system GroEL-GroES is present in all kingdoms of life and rescues proteins from improper folding and aggregation upon internal and external stress conditions, including high temperatures and pressures. Here, we set out to explore the thermo- and piezostability of GroEL, GroES and the GroEL-GroES complex in the presence of cosolvents, nucleotides and salts employing quantitative FTIR spectroscopy and small-angle X-ray scattering. Owing to its high biological relevance and lack of data, our focus was especially on the effect of pressure on the chaperonin system. The experimental results reveal that the GroEL-GroES complex is remarkably temperature stable with an unfolding temperature beyond 70 °C, which can still be slightly increased by compatible cosolutes like TMAO. Conversely, the pressure stability of GroEL and hence the GroEL-GroES complex is rather limited and much less than that of monomeric proteins. Whereas GroES is pressure stable up to ∼5 kbar, GroEl and the GroEl-GroES complex undergo minor structural changes already beyond 1 kbar, which can be attributed to a dissociation-induced conformational drift. Quite unexpectedly, no significant unfolding of GroEL is observed even up to 10 kbar, however, i.e., the subunits themselves are very pressure stable. As for the physiological relevance, the structural integrity of the chaperonin system is retained in a relatively narrow pressure range, from about 1 to 1000 bar, which is just the pressure range encountered by life on Earth.

Tubulin is one of the main components of the cytoskeleton of eukaryotic cells. The formation of microtubules depends strongly on environmental and solution conditions, and has been found to be among the most pressure sensitive processes in vivo. We explored the effects of different types of cosolvents, such as trimethylamine-N-oxide (TMAO), sucrose and urea, and crowding agents to mimic cell-like conditions, on the temperature and pressure stability of the building block of microtubules, i. e. the α/β-tubulin heterodimer. To this end, fluorescence and FTIR spectroscopy, differential scanning and pressure perturbation calorimetry as well as fluorescence anisotropy and correlation spectroscopies were applied. The pressure and temperature of dissociation of α/β-tubulin as well as the underlying thermodynamic parameters upon dissociation, such as volume and enthalpy changes, have been determined for the different solution conditions. The temperature and pressure of dissociation of the α/β-tubulin heterodimer and hence its stability increases dramatically in the presence of TMAO and the nanocrowder sucrose. We show that by adjusting the levels of compatible cosolutes and crowders, cells are able to withstand deteriorating effects of pressure even up to the kbar-range.

Deep subsurface environments can harbour high concentrations of dissolved ions, yet we know little about how this shapes the conditions for life. We know even less about how the combined effects of high pressure influence the way in which ions constrain the possibilities for life. One such ion is perchlorate, which is found in extreme environments on Earth and pervasively on Mars. We investigated the interactions of high pressure and high perchlorate concentrations on enzymatic activity. We demonstrate that high pressures increase α-chymotrypsin enzyme activity even in the presence of high perchlorate concentrations. Perchlorate salts were shown to shift the folded α-chymotrypsin phase space to lower temperatures and pressures. The results presented here may suggest that high pressures increase the habitability of environments under perchlorate stress. Therefore, deep subsurface environments that combine these stressors, potentially including the subsurface of Mars, may be more habitable than previously thought., Gault et al. show that high pressures increase α-chymotrypsin enzyme activity in the presence of high perchlorate concentrations. These perchlorate salts shift the folded enzyme phase space to lower temperatures and pressure and may move the optimum enzyme activity towards lower temperatures in addition to higher pressures, which has implications for Martian habitability.

The arginine binding protein from T. maritima (ArgBP) exhibits several distinctive biophysical and structural properties. Here we show that ArgBP is also endowed with a ramarkable pressure stability as it undergoes minor structural changes only, even at 10 kbar. A similar stability is also observed for its folded fragments (truncated monomer and individual domains). A survey of literature data on the pressure stability of proteins highlights the uncommon behavior of ArgBP.

We report on the effects of pressure and cosolvents on the catalytic activity of a designed amyloid fibril by applying a high-pressure stopped-flow methodology with rapid spectroscopic detection. FTIR spectroscopic data revealed a remarkable pressure and temperature stability of the fibrillar catalyst. The activity is further enhanced by osmolytes and macromolecular crowding.

Actin and tubulin, the main components of the cytoskeleton, are responsible for many different cellular functions and can be found in nearly all eukaryotic cells. The formation of filamentous actin (F-actin) as well as microtubules depends strongly on environmental and solution conditions. The self-assembly of both, actin and tubulin, has been found to be among the most pressure sensitive process in vivo. Here, we explored the effects of various types of natural cosolvents, such as urea and the osmolyte trimethylamine-N-oxide (TMAO), on the temperature- and pressure-dependent stability of their polymeric states, F-actin and microtubules. Accumulation of TMAO by deep-sea animals is proposed to protect against destabilizing effects of pressure. The pressure and temperature of unfolding as well as associated enthalpy and volume changes have been determined using Fourier-transform infrared spectroscopy, covering a wide range of pressures and temperatures, ranging from 1 bar to 11 kbar and from 20 to 90 °C, respectively. Complementary thermodynamic measurements have been carried out using differential scanning and pressure perturbation calorimetry. The results obtained helped us explore the effect of the cellular milieu on the limitations of the pressure stability of cytoskeletal assemblies. Conversely to urea, the pressure stability of both polymers increases dramatically in the presence of TMAO, counteracting detrimental effects of both, urea and pressure.

High pressure is an important feature of certain natural environments, such as the deep sea where pressures up to about 1000 bar are encountered. Further, pressure effects on biosystems are of increasing interest for biotechnological applications, such as baroenzymology. We studied the effect of two different natural osmolyte mixtures, with major components being glycine and trimethylamine-N-oxide (TMAO), on the activity of α-chymotrypsin, using high-pressure stopped-flow methodology in combination with fast UV/Vis detection. We show that pressure is not only able to drastically enhance the catalytic activity and efficiency of the enzyme, but also that glycine has a significant and diverse effect on the enzymatic activity and volumetric properties of the reaction compared to TMAO. The results might not only help to understand the modulation of enzymatic reactions by natural osmolytes, but also elucidate ways to optimize enzymatic processes in biotechnological applications.