Factors determining protein thermostability

Proteins, independent of their mesophilic or extremophilic origin, consist exclusively of the 20 canonical natural amino acids. It is therefore interesting to understand the reasons how some proteins are stabilized so as to resist exceptional temperatures. 

Despite these numerous studies, it is still a matter of debate as to which structural factors are the main determinants of the increased stability in thermostable proteins. There are substantial differences between the 

Better packing, smaller and less numerous cavities 53-55 

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A number of factors may affect enzyme stabihty in vivo. Certain enzymes from thermophiles have been shown to be less stable in the pure state or in cell-free extracts than in vivo, integrity being enhanced by factors in the cellular environment [29], such as high protein concentration, substrates, prosthetic groups and other molecules [30-34]. The fact remains, however, that thermophUic enzymes as a class are inherently more thermostable than their mesophilic counterparts, and that this stability is primarily intrinsic rather than being determined by extrinsic factors. 

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