How do thermophilic proteins deal with heat?

Abstract

Recent years have witnessed an explosion of sequence and structural information for proteins from hyperthermophilic and thermophilic organisms. Complete genome sequences are available for many hyperthermophilic archaeons. Here, we review some recent studies on protein thermostability along with work from our laboratory. A large number of sequence and structural factors are thought to contribute toward higher intrinsic thermal stability of proteins from these organisms. The most consistent are surface loop deletion, increased occurrence of hydrophobic residues with branched side chains and an increased proportion of charged residues at the expense of uncharged polar residues. The energetic contribution of electrostatic interactions such as salt bridges and their networks toward protein stability can be stabilizing or destabilizing. For hyperthermophilic proteins, the contribution is mostly stabilizing. Macroscopically, improvement in electrostatic interactions and strengthening of hydrophobic cores by branched apolar residues increase the enthalpy change between the folded and unfolded states of a thermophilic protein. At the same time, surface loop deletion contributes to decreased conformational entropy and decreased heat capacity change between the folded and unfolded states of the protein.

Crystal Structure of a Bacterial Endospore Coat Component

“…Thermostability Versus Structure-Factors enhancing protein thermostability have been extensively reviewed elsewhere by the study of test case thermophilic proteins in comparison with their mesophilic counterparts (56). Several factors including hydrogen bonds and salt bridges, distribution of charged residues on the surface, protein packing, and amino acid composition have been postulated to be involved in the increased thermostability properties of some enzymes belonging to thermophilic microorganisms (57). In the particular case of CotA, all these factors were carefully analyzed in comparison with other monomeric multicopper oxidases of known three-dimensional structure.…”

Role of Internal Water on Protein Thermal Stability: The Case of Homologous G Domains

“…Several molecular factors ensure this extreme stability and their combination results in different thermodynamic strategies for thermal adaptation [1][2][3][4] . With respect to their mesophilic homologues, (hyper)thermophiles are generally enriched in charged amino-acids and cross-linked by a larger number of hydrogen bonds (HB) and salt-bridges that contribute to stabilize the protein fold [5][6][7] .…”

“…With respect to their mesophilic homologues, (hyper)thermophiles are generally enriched in charged amino-acids and cross-linked by a larger number of hydrogen bonds (HB) and salt-bridges that contribute to stabilize the protein fold [5][6][7] . They have shorter loops that protect the fold from thermal excitation by reducing the extension of weak spots at the protein surface [2][3][4]8,9 . Moreover, an optimized and extended hydrophobic packing in the protein core or at domain interfaces enhances the intramolecular cohesive forces 10 .…”

Thermal effects on microbial composition and microbiologically induced corrosion and mineral precipitation affecting operation of a geothermal plant in a deep saline aquifer

“…Elevated temperature and high salinity create harsh living conditions for microbes. Only specific microorganisms subsist at these elevated temperatures and high salinity due to modifications in proteins, DNA, and cell membrane composition as well as intracellular accumulation of low molecular compounds (Aerts et al 1985;Kempf and Bremer 1998;Kumar and Nussinov 2001;Roberts 2005). Moreover, some microorganisms are able to get into a dormancy stage by forming spores, cysts or other types of resting cells and survive starvation, exposure to extreme temperatures, and elevated background radiation (Burke and Wiley 1937;Amy 1997;Suzina et al 2004;Johnson et al 2007).…”