PAI-1 stability: the role of histidine residues.
The role of the 13 histidine residues in plasminogen activator inhibitor 1 (PAI-1) for the stability of the molecule was studied by replacing these residues by threonine, using site-directed mutagenesis. The generated mutants were expressed in Escherichia coli, purified and characterized. All variants had a normal activity and formed stable complexes with tissue-type plasminogen activator. Most of these PAI-1 variants displayed a similar pH-dependency in stability as wild-type PAI-1, with increased half-lives at lower pH. However, the variant His364Thr had a half-life of about 50 min at 37 degrees C and had almost completely lost its pH-dependency. Therefore, our data suggest that His(364), in the COOH-terminal end of the molecule might be responsible for the pH-dependent stability of PAI-1.
Mångs
H
H
Department of Clinical Chemistry and Blood Coagulation, Karolinska Hospital, Karolinska Institute, S-171 76, Stockholm, Sweden.
Sui
G C
GC
Wiman
B
B
D019943:Amino Acid Substitution; D004926:Escherichia coli; D006639:Histidine; D006801:Humans; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry* / Q000235:genetics; D017354:Point Mutation; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship
D017395:Plasminogen Activator Inhibitor 1; D015842:Serine Proteinase Inhibitors; D006639:Histidine