The two-domain structure of streptokinase (Sk) was demonstrated by scanning calorimetric investigations at neutral pH and low ionic strength. The melting pattern of the protein is composed of two two-state transitions at TtrS1 = 45.9 +/- 0.4 degrees C with delta H1 = 431 +/- 18 kJ/mol, and TtrS2 = 60.1 +/- 1.3 degrees C with delta H2 = 306 +/- 16 kJ/mol. The partial specific heat capacity of native Sk was determined to be Cp = 1.42 +/- 0.17 J/K/g and the denaturational heat capacity change associated with the two transitions, delta Cp1 = 0.21 J/K/g and delta Cp2 = 0.38 J/K/g, respectively. The overall melting pattern of Sk remains almost unchanged at a variety of tested solvent compositions, except at pH 4 (and below) and in the presence of denaturants. The two domains show different susceptibility to urea. It is proposed that the less thermostable domain is located within the N-terminal part (residues 1-230), and the more thermostable one, within the C-terminal region. Study holds ProTherm entries: 9791, 9792, 9793 Extra Details: transition 1 streptokinase; domain structure; calorimetry
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:38 p.m.
|Number of data points||6|
|Proteins||Streptokinase C ; Streptokinase C|
|Assays/Quantities/Protocols||Experimental Assay: dHcal pH:4.0 ; Experimental Assay: Tm pH:4.0 ; Experimental Assay: dHcal pH:7.5 ; Experimental Assay: Tm pH:7.5|
|Libraries||Mutations for sequence IQNQAKSVDVEYTVQFTPLNPDDDFRPGLKLTKLLKTLAIGDTITSQELLAQAQSILNKNHPGYTIYERDSSIVTHDNDIFRTILPMDQEFTYRVKNREQAYRINKKSGLNEEINNTDLISEKYYVLKKGEKPYDPFD|