Hsp 90

In chunkdz's thread about Behe, irreducible complexity and more at Telic Thoughts a commenter and fellow MMA fan named computerist referenced a paper authored by Helen Pickersgill. It is slightly confusing in that the journal Cell Biology (Hidden Change) is mentioned at the top of the quote and PLOS Biology at the Bottom. In any case the quote is as follows:

Biological systems are buffered against variation by proteins termed phenotypic capacitors, of which heat shock protein 90 (Hsp90) is the founding member. This protein chaperone reveals diverse phenotypic variation when its level falls, exposing previously silenced genotypes. Given that species advancement requires genetic diversity and phenotypic change, phenotypic capacitors have been suggested to support evolution; the reduction of Hsp90, which occurs under stressful conditions, would release phenotypes that can be acted on by natural selection to drive evolution. Whether other cellular proteins harbor capacitor function is unclear. Levy and Siegel used high-throughput morphological phenotyping and found that more than 5% of yeast genes act as capacitors by buffering environmental variation and suppressing phenotypic diversity. These capacitors were found to control cellular processes, such as cell cycle regulation and stress responses. Beyond a role in natural selection, phenotypic capacitors may also support the evolution of cancer cells, which are notoriously resilient to many environmental stresses and exhibit widespread genetic instability. Hsp90 is thought to buffer these tumorigenic properties and promote survival, and Hsp90 inhibitors may have potential as cancer chemotherapeutics.

There's enough to induce one to locate and read the full paper.