Folding Filaments

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Science  11 Apr 2003:
Vol. 300, Issue 5617, pp. 215
DOI: 10.1126/science.300.5617.215d

Under conditions that would blow apart the cells of metazoans, many Archaea and Eubacteria achieve remarkable feats of endurance with subtle, almost undetectable changes in biochemistry and physiology. It has been thought that, under stressful conditions, chaperonins are induced to refold damaged proteins, but Kagawa et al. contest this belief. Chaperonins are composed of heat shock protein (Hsp60) subunits that assemble into double ring structures. The hyperthermophilic archaean Sulfolobus shibatae likes to grow at about 80°C. When it is exceptionally hot (>86°C), these rings are composed mainly of Hsp subunits alpha and beta, which assemble into rings that then form filaments. When it's cooler (<60°C), the proportion containing gamma Hsp subunits increases; this combination is less stable, and shorter, more flexible filaments form, which may have more to do with membrane stability or fluidity than protein folding.—CA

Mol. Microbiol.48, 143 (2003).

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