Single-Molecule Spectroscopy of Cold Denaturation
and the Temperature-Induced Collapse of Unfolded Proteins
- Publication date
- Publisher
Abstract
Recent Förster resonance energy
transfer (FRET) experiments
show that heat-unfolded states of proteins become more compact with
increasing temperature. At the same time, NMR results indicate that
cold-denatured proteins are more expanded than heat-denatured proteins.
To clarify the connection between these observations, we investigated
the unfolded state of yeast frataxin, whose cold denaturation occurs
at temperatures above 273 K, with single-molecule FRET. This method
allows the unfolded state dimensions to be probed not only in the
cold- and heat-denatured range but also in between, i.e., in the presence
of folded protein, and can thus be used to link the two regimes directly.
The results show a continuous compaction of unfolded frataxin from
274 to 320 K, with a slight re-expansion at higher temperatures. Cold-
and heat-denatured states are thus essentially two sides of the same
coin, and their behavior can be understood within the framework of
the overall temperature dependence of the unfolded state dimensions