But my point is that epigenetic processes control if genes go on or off, they do not change the prevalence of the gene in the population like natural selection does, or change the protein coded for by the gene the way mutation does.
Here is the study whereby mutations which changed three amino acids led to a heat stable xylanase protein....
Thermal stabilization of Bacillus subtilis family-11 xylanase by directed evolution.Miyazaki K, Takenouchi M, Kondo H, Noro N, Suzuki M, Tsuda S.
Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan. miyazaki-kentaro@aist.go.jp
We used directed evolution to enhance the thermostability of glycosyl hydrolase family-11 xylanase from Bacillus subtilis. By combining random point mutagenesis, saturation mutagenesis, and DNA shuffling, a thermostable variant, Xyl(st), was identified which contained three amino acid substitutions: Q7H, N8F, and S179C. The half-inactivation temperature (the midpoint of the melting curves) for the Xyl(st) variant compared with the wild-type enzyme after incubation for 10 min was elevated from 58 to 68 degrees C. At 60 degrees C the wild-type enzyme was inactivated within 5 min, but Xyl(st) retained full activity for at least 2 h. The stabilization was accompanied by evidence of thermophilicity; that is, an increase in the optimal reaction temperature from 55 to 65 degrees C and lower activity at low temperatures and higher activity at higher temperatures relative to wild type. To elucidate the mechanism of thermal stabilization, three-dimensional structures were determined for the wild-type and Xyl(st) enzymes. A cavity was identified around Gln-7/Asn-8 in wild type that was filled with bulky, hydrophobic residues in Xyl(st). This site was not identified by previous approaches, but directed evolution identified the region as a weak point. Formation of an intermolecular disulfide bridge via Cys-179 was observed between monomers in Xyl(st). However, the stability was essentially the same in the presence and absence of a reducing agent, indicating that the increased hydrophobicity around the Cys-179 accounted for the stability.
PMID: 16467302 [PubMed - indexed for MEDLINE]
==I was just looking for it....
Did you find anything yet? Unless we are talking about two different subjects, your contention that epigenetics has nothing to do with heat stress proteins is clearly in error. Here’s another paper on the crucial role epigenetics plays with respect to heat stress proteins:
Evidence for an epigenetic mechanism by which Hsp90 acts as a capacitor for morphological evolution
Morphological alterations have been shown to occur in Drosophila melanogaster when function of Hsp90 (heat shock 90-kDa protein 1, encoded by Hsp83) is compromised during development1. Genetic selection maintains the altered phenotypes in subsequent generations1. Recent experiments have shown, however, that phenotypic variation still occurs in nearly isogenic recombinant inbred strains of Arabidopsis thaliana 2. Using a sensitized isogenic D. melanogaster strain, iso-Kr If-1, we confirm this finding and present evidence supporting an epigenetic mechanism for Hsp90’s capacitor function, whereby reduced activity of Hsp90 induces a heritably altered chromatin state. The altered chromatin state is evidenced by ectopic expression of the morphogen wingless in eye imaginal discs and a corresponding abnormal eye phenotype, both of which are epigenetically heritable in subsequent generations, even when function of Hsp90 is restored. Mutations in nine different genes of the trithorax group that encode chromatin-remodeling proteins also induce the abnormal phenotype. These findings suggest that Hsp90 acts as a capacitor for morphological evolution through epigenetic and genetic mechanisms.
http://www.nature.com/ng/journal/v33/n1/abs/ng1067.html