Irreversible thermal denaturation of Trichoderma reesei endo-1,4-beta-xylanase II and its three disulfide mutants characterized by differential scanning calorimetry.
Kinetic as well as energetic aspects of the thermal denaturation of Trichoderma reesei endo-1,4-beta-xylanase II (TRX II) and its three thermostable disulfide mutants were characterized by means of differential scanning calorimetry (DSC) in different solution conditions. The calorimetric transitions were strongly scan-rate dependent, characteristic for an irreversible, kinetically controlled protein denaturation. The DSC-determined T*-values (the temperature at which the denaturation rate constant equals 1min(-1)), and the activation free energies for the transitions are consistent with the apparent transition temperatures of TRX II determined earlier by mass spectrometry. Protein aggregation, connected with the irreversibility of the transitions, was present in all cases but was less pronounced with the mutants as well as highly dependent on experimental conditions.
Jänis
Janne
J
University of Joensuu, Department of Chemistry, PO Box 111, FI-80101 Joensuu, Finland. jjanis@cc.joensuu.fi
Rouvinen
Juha
J
Vainiotalo
Pirjo
P
Turunen
Ossi
O
Shnyrov
Valery L
VL
D000085:Acetates / Q000737:chemistry; D002021:Buffers; D002152:Calorimetry, Differential Scanning; D004220:Disulfides; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D044366:Transition Temperature; D014242:Trichoderma / Q000201:enzymology*
D000085:Acetates; D002021:Buffers; D004220:Disulfides; D005656:Fungal Proteins; D043364:Endo-1,4-beta Xylanases; C018824:ammonium acetate