Some Like It Hot

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Science  09 Sep 2005:
Vol. 309, Issue 5741, pp. 1653
DOI: 10.1126/science.309.5741.1653a

Ever since atomic-resolution models of enzymes from thermophilic organisms appeared a decade ago, one question has been how these macromolecules are able to function (that is, remain flexible) while maintaining their integrity (that is, remain stable) at temperatures approaching 100°C. Some of the explanations offered are an increase (relative to their mesophilic cousins) in the number of salt bridges and/or hydrogen bonds, a tighter packing of the hydrophobic core, and a higher percentage of amino acids incorporated into α helices and α sheets.

Berezovsky and Shakhnovich have carried out unfolding simulations on matched proteins from mesophiles and thermophiles, and performed comparative genome-based analysis of mesophilic and thermophilic bacteria and archaea. They find two solutions for thriving at high temperatures: make protein structure more compact by optimizing relatively weak interactions globally or engineer a few strong interactions into the sequence. They suggest that archaeal thermophiles (Pyrococcus furiosus) were favored by starting off long ago with more designable proteins that could be adapted to the primordial hothouse, whereas bacterial thermophiles (Thermotoga maritima) that entered hot environments later on were forced to reinforce their proteins with staples (salt bridges or perhaps disulfides). — GJC

Proc. Natl. Acad. Sci. U.S.A. 102, 12742 (2005).

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