Role of residual structure in the unfolded state of a thermophilic protein

AUTOR(ES)

Robic, Srebrenka

FONTE

National Academy of Sciences

RESUMO

Ribonucleases H from the thermophilic bacterium Thermus thermophilus and the mesophile Escherichia coli demonstrate a dramatic and surprising difference in their change in heat capacity upon unfolding (ΔCp°). The lower ΔCp° of the thermophilic protein directly contributes to its higher thermal denaturation temperature (Tm). We propose that this ΔCp° difference originates from residual structure in the unfolded state of the thermophilic protein; we verify this hypothesis by using a mutagenic approach. Residual structure in the unfolded state may provide a mechanism for balancing a high Tm with the optimal thermodynamic stability for a protein's function. Structure in the unfolded state is shown to differentially affect the thermodynamic profiles of thermophilic and mesophilic proteins.

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