A differential scanning calorimetric investigation of the domains of recombinant tissue plasminogen activator.
The differential scanning calorimetric (DSC) properties of a series of recombinant tissue plasminogen activators (rt-PA) have been examined. The endotherm obtained for native rt-PA can be deconvoluted into a pair of two-state transitions, which indicates that two separate observable regions of the molecule undergo independent melting. A distinguishing feature of native rt-PA is the dependence of the temperature of the maximum heat capacity of the endothermic transitions (Tm) on the thermal scan rate of the samples, suggesting that a kinetic process, involving conversion of a reversibly denatured to an irreversibly denatured form of the protein, with an energy of activation of approximately 81.5 kcal/mol, characterizes its thermal denaturation. A comparison of the conformational properties of rt-PA preparations which have been produced in different expression systems, as revealed by DSC analysis of their thermal denaturation characteristics, has demonstrated that subtle differences do occur. Similar studies with deletion mutants of rt-PA suggest that the growth factor domain (EGF) plays a role in its overall thermal stability, when the protein also contains the kringle 1 region, and removal of the EGF domain leads to conformational alterations in other areas of the molecule.
Radek
J T
JT
Department of Chemistry, University of Notre Dame, Indiana 46556.
Castellino
F J
FJ
D002152:Calorimetry, Differential Scanning; D004735:Energy Transfer; D006863:Hydrogen-Ion Concentration; D008433:Mathematics; D009154:Mutation; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000032:analysis; D013696:Temperature; D010959:Tissue Plasminogen Activator / Q000032:analysis* / Q000235:genetics
D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator