Submitted on September 27, 2004
Accepted on January 5, 2005
Comparison of Hsc70 orthologues from polar and temperate notothenioid fishes: Differences in the prevention of aggregation and refolding of denatured proteins
Sean P Place1* and Gretchen E Hofmann1
1 Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA; Marine Science Institute, University of California, Santa Barbara, CA, USA
* To whom correspondence should be addressed. E-mail: place{at}lifesci.ucsb.edu.
Although a great deal is known about the cellular function of molecular chaperones in general, very little is known about the effect of temperature selection on the function of molecular chaperones in non-model organisms. One major unanswered question is whether orthologous variants of a molecular chaperone from differential thermally adapted species vary in their thermal responses. In order to address this issue, we utilized a comparative approach to examine the temperature interactions of a major cytosolic molecular chaperone, Hsc70, from differently thermally adapted notothenioids. Using in vitro assays, we measured the ability of Hsc70 to prevent thermal aggregation of lactate dehydrogenase (LDH). We further compared the capacity of Hsc70 to refold chemically denatured LDH over the temperature range of -2 °C to +45 °C. Hsc70 purified from the temperate species exhibited greater ability to prevent the thermal denaturation of LDH at 55 °C compared to Hsc70 from the cold adapted species. Furthermore, Hsc70 from the Antarctic species lost the ability to competently refold chemically denatured LDH at a lower temperature when compared to Hsc70 from temperate species. These data indicate the function of Hsc70 in notothenioid fishes maps onto their thermal history and that temperature selection has acted on these molecular chaperones.
