[ccp4bb]: Thermostability vs Structure

[Rudolf Ladenstein <Rudolf.Ladenstein@csb.ki.se>]

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Dear Francisco,

There seems indeed to exist a strong and general interest on protein
stability/thermostability, which makes me happy and shows that we are on
the right track with our own research...

Concerning "kinetic stability" and "thermodynamic stability", one often can
see that people misuse or mix up these terms, they have to be separated
carefully, because they mean different things and often are not even
correlated in protein structures, for instance one can have an enzyme
structure which is catalytically "dead" in kinetic assays and still show a
high value of the melting temperature.

Certainly one can try to approach measurements of thermodynamic stability
in proteins by carefully selected mutants and the analysis of multiple
thermodynamic cycles as shown by Fersht & Horovitz and others, but these
measurements are not as straightforward as one might think, because your
protein needs to unfold by a reversible unfolding/folding equilibrium (not
many of the large enzymes or protein oligomers are ready to do that for
you!) and you have always to show that there are in fact no structural
differences between the wild type and the mutant protein, which would need
X-ray analysis of the mutants and careful refinement at high resolution...

I do not think, that your problem is close to unsolvable, but you need a
careful planning of the experimental approach, and your system must have
certain properties to be suitable for kinetic and especially thermodynamic
analysis, usually by CD- or Fluorescence spectroscopy and/or Calorimetry

with kind regards,

Rudolf Ladenstein
Professor of Structural Biochemistry
Karolinska Institutet NOVUM
Dept. of Biosciences
S-14157 Huddinge, Sweden