The thermal stability of two xylanases with molecular masses of 45 (Xys1L) and 35 (Xys1S) kDa has been characterized thermodynamically by high-sensitivity scanning microcalorimetry in the pH range 3.0-9.0. Thermal denaturation of Xys1L reveals three thermodynamically independent domains, and that of Xys1S, which is a proteolytic fragment of Xys1L (without a C-terminal part), reveals two thermodynamically independent domains, each of which follows a two-state thermal unfolding process under our experimental conditions. Nevertheless, the thermodynamic parameters of unfolding for each domain do not fit some of the correlations obtained for most compact globular proteins. It is known that if delta Hres(T) and delta Sres(T) are plotted against temperature for a number of water-soluble compact globular proteins, they all have a common value at approximately 110 degrees C (383 K). Calculation of the variations in the enthalpy and entropy of unfolding per residue for each domain of xylanase with temperature gave us delta Hres(383) and delta Sres(383) values of approximately 3 kcal/(mol of residue) and 9 cal/(K.mol of residue), respectively. This is practically 2-fold larger than those apparent for most medium-sized globular protein values. These discrepancies might be related to features of the folded and/or unfolded states of the protein. Study holds ProTherm entries: 4447, 4448, 4449, 4450, 4451, 4452, 4453, 4454, 4455, 4456, 4457, 4458, 4459, 4460, 4461, 4462, 4463, 4464 Extra Details: transition 1 thermodynamically independent domains;,two-state thermal unfolding; compact globular proteins; enthalpy
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:25 p.m.
|Number of data points||36|
|Assays/Quantities/Protocols||Experimental Assay: dHcal pH:4.1 ; Experimental Assay: Tm pH:4.1 ; Experimental Assay: dHcal pH:8.9, buffers:glycine-NaOH: 60 mM ; Experimental Assay: Tm pH:8.9, buffers:glycine-NaOH: 60 mM ; Experimental Assay: dHcal pH:7.5 ; Experimental Assay: Tm pH:7.5 ; Experimental Assay: dHcal pH:6.3 ; Experimental Assay: Tm pH:6.3 ; Experimental Assay: dHcal pH:3.6 ; Experimental Assay: Tm pH:3.6|
|Libraries||Mutations for sequence MQQDGKRQDQNQQNPAPFSGLSRRGFLGGAGTVALATASGLLLPSTAHAATTITTNQTGYDGMYYSFWTDGGGSVSMTLNGGGSYSTQWTNCGNFVAGKGWGNGGRRTVRYSGYFNPSGNGYGCLYGWTSNPLVEYYIVDNWGSYRPTGEYRGTVYSDGGTYDIYKTTRYNAPSVEGTRTFDQYWSVRQSKVIGSGTITTGNHFDAWARAGMNLGQFQYYMIMATEGYQSSGSSNITVSG|