The three-dimensional structure of the basic pancreatic trypsin inhibitor (BPTI) contains four internal water molecules, which form a total of nine intermolecular hydrogen bonds with the BPTI polypeptide chain. To investigate the effect of such internal hydration on protein structure and stability, we displaced one of the internal water molecules in a recombinant BPTI analogue, BPTI(G36S), in which Gly 36 is replaced by serine. The replacement of a water molecule by the seryl side chain was established by the absence of the protein-water nuclear Overhauser effects (NOE) that had been attributed to the water molecule near Gly 36 in wild-type BPTI and by the presence of new, intramolecular NOEs to the hydroxyl proton of Ser 36. BPTI(G36S) has slightly reduced thermal stability compared to BPTI, corresponding to a destabilization by delta (delta G) approximately 0.7 kcal/M in 6 M guanidinium hydrochloride solution. Additionally, the stabilities of the complexes formed between BPTI(G36S) and trypsin, plasmin, or kallikrein are significantly reduced when compared to the corresponding complexes with wild-type BPTI. Study holds ProTherm entries: 300, 301, 13294 Extra Details: internal hydration; protein structure; thermal stability; BPTI
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:14 p.m.
|Number of data points||7|
|Proteins||Pancreatic trypsin inhibitor ; Pancreatic trypsin inhibitor|
|Assays/Quantities/Protocols||Experimental Assay: ddG ; Experimental Assay: Tm ; Experimental Assay: dHvH ; Derived Quantity: dTm|
|Libraries||Mutations for sequence RPDFCLEPPYTGPCKARIIRYFYNAKAGLCQTFVYGGCRAKRNNFKSAEDCMRTCGGA|