Effect of phospholipids on conformational structure of bovine pancreatic trypsin inhibitor (BPTI) and its thermolabile mutants.

The effects of negatively charged phosphatidylserine-prepared membranes (PS) and neutral phosphatidylcholine-prepared membranes (PC) on the structure of wild-type and mutant bovine pancreatic trypsin inhibitor (BPTI) at neutral pH were investigated. The presence of PC did not have any effect on the protein structure while PS induced a non-native structure in three mutant BPTI proteins. However, the negatively charged membrane did not have any effect on wild-type BPTI.

Biophysical analysis of heat-induced structural maturation of glutamate dehydrogenase from a hyperthermophilic archaeon.

Tertiary structure of the recombinant glutamate dehydrogenase from Thermococcus kodakaraensis KOD1 (Tk-rGDH) converts into an intact form induced by the heat treatment. This phenomenon, heat-induced structural maturation, means that high temperature plays an important role in the proper folding and oligomerization of Tk-rGDH. In this work, we analyzed the heat-induced structural maturation of Tk-rGDH by differential scanning microcalorimetry (DSC), circular dichroism (CD), and activity measurements.

Mutational effects on O(6)-methylguanine-DNA methyltransferase from hyperthermophile: contribution of ion-pair network to protein thermostability.

Ion pairs have been considered to be general stabilizing factors in hyperthermophilic proteins, but the present experimental data cannot fully explain how ion pairs and ion-pair networks contribute to the stability. In this paper, we show experimental evidence that not all of the internal ion pairs contribute to the thermal and thermodynamic stability, using O(6)-methylguanine-DNA methyltransferase from Thermococcus kodakaraensis KOD1 (Tk-MGMT) as a model protein. Of three mutants in which an inter-helical ion pair was disrupted, only one mutant (E93A) was shown to be destabilized.