The thermal stability of Taq DNA polymerase is well known, and is the basis for its use in PCR.  Comparative thermodynamic characterization of the large fragment domains of Taq (Klentaq) and E. coli (Klenow) DNA polymerases reveals that Klentaq's extreme free energy of folding (?Gfold) originates from a significantly decreased entropic folding penalty (?Sconf).  In-solution structural analyses of the denatured-state ensembles of the two proteins demonstrate a significantly smaller and less solvent accessible denatured state for Klentaq relative to Klenow, in contrast to the currently held view that denatured state size depends only upon chain length.  The smaller denatured state size of Klentaq correlates well with a decreased entropic folding penalty.  Despite the larger denatured state size for Klenow, both still fall within the range for random-coil behavior.   This is the first direct structural comparison of the denatured states of a homologous mesophilic-thermophilic protein pair.

Entropic and structural origins for the extreme stability of Taq DNA polymerase

243rd National Meeting (2012)

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