Polymerization of plasminogen activator inhibitor-1.
The activity of the serine proteinase inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) is controlled by the intramolecular incorporation of the reactive loop into beta-sheet A with the generation of an inactive latent species. Other members of the serpin superfamily can be pathologically inactivated by intermolecular linkage between the reactive loop of one molecule and beta-sheet A of a second to form chains of polymers associated with diverse diseases. It has long been believed that PAI-1 is unique among active serpins in that it does not form polymers. We show here that recombinant native and latent PAI-1 spontaneously form polymers in vitro at low pH although with distinctly different electrophoretic patterns of polymerization. The polymers of both the native and latent species differ from the typical loop-A-sheet polymers of other serpins in that they readily dissociate back to their original monomeric form. The findings with PAI-1 are compatible with different mechanisms of linkage, each involving beta-strand addition of the reactive loop to s7A in native PAI-1 and to s1C in latent PAI-1. Glycosylated native and latent PAI-1 can also form polymers under similar conditions, which may be of in vivo importance in the low pH environment of the platelet.
Zhou
A
A
Department of Haematology, University of Cambridge, Wellcome Trust Centre for Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 2XY, United Kingdom. awz20@cus.cam.ac.uk
Faint
R
R
Charlton
P
P
Dafforn
T R
TR
Carrell
R W
RW
Lomas
D A
DA
D000595:Amino Acid Sequence; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
D001704:Biopolymers; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins