title: Conformational properties of streptokinase--differential scanning calorimetric investigations.
abstract: 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.
authors.affiliation: Department of Molecular Biophysics, Central Institute of Molecular Biology, Berlin-Buch, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Welfle
authors.forename: W
authors.initials: W
authors.lastname: Pfeil
authors.forename: R
authors.initials: R
authors.lastname: Misselwitz
authors.forename: H
authors.initials: H
authors.lastname: Welfle
authors.forename: D
authors.initials: D
authors.lastname: Gerlach
mesh_terms: D000596:Amino Acids; D002152:Calorimetry, Differential Scanning / Q000379:methods; D011487:Protein Conformation; D013291:Streptococcus / Q000201:enzymology; D013300:Streptokinase / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D013300:Streptokinase