Extrinsic factors stabilizing the native state of proteins at high temperatures

Extrinsic factors stabilizing the native state of proteins at high temperatures 

As is generally known, the conformational stability of proteins depends on intramolecular interactions and on environmental factors (the surrounding solvent different low-and high-molecular weight compounds). Often, the thermostability of isolated proteins measured in vitro is unexpectedly low, suggesting that the in vitro conditions are lacking stabilizing factors present in vivo. 

Interestingly, high K concentration could also be found in P. woesei (600mM[10]) counterbalanced by a new, not yet described phosphoderivative of inositol. Like the potassium salt of cDPG this potassium salt also increases the thermostability of proteins [107]. 

In organisms without strikingly high intracellular ion concentrations (e.g. members of the Crenarchaeota), some of their proteins show a low intrinsic stability in vitro (e.g., aminopeptidase from S. solfataricus [36] or endonuclease Sual from S. acidocaldarius [37]), suggesting that more or less specific interactions with other cell constituents are likely important to stabilize the native state of the intracellular enzymes at high temperatures. 

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