Title: Conformational studies on plasminogen-activator inhibitor (pai-1) in active, latent, substrate, and cleaved forms
Authors: Sancho, E ×
Declerck, Paul
Price, Nc
Kelly, Sm
Booth, Na #
Issue Date: Jan-1995
Publisher: Amer chemical soc
Series Title: Biochemistry vol:34 issue:3 pages:1064-1069
Abstract: Plasminogen activator inhibitor 1 (PAI-1), the primary physiological inhibitor of t-PA, is an unusual member of the serpin family of serine protease inhibitors, in that it spontaneously converts to a latent form. Latent PAI-1 has been reported to share characteristics with the cleaved form of other serpins. Here we examine the conformation of four forms of PAI-1, active and latent wild-type, together with a noninhibitory, substrate mutant that is cleavable at P-1-P-1', and its cleaved product. The circular dichroism spectra of active and latent PAI-1 showed differences consistent with decreased alpha-helix from 26% to 22% and increased beta-sheet from 23% to 34% as active --> latent. Active and substrate PAI-1 were less thermostable than latent PAI-1, which was 50% denatured at 70 degrees C. In contrast, cleaved PAI-1 was very stable, with little loss of structure at 100 degrees C. Cleaved PAI-1 was much more resistant to guanidinium chloride (Gdn-HCl), 50% unfolding requiring 4.5 M Gdn-HCl, while active, latent, and substrate forms of PAI-1 were 50% unfolded in 2-2.5 M Gdn-HCl. The differences in fluorescence emission maxima, latent 339 nm, active 336 nm, substrate 343 nm, and cleaved 333 nm, underline the contrast between latent and cleaved PAI-1. The conformational changes occurring on cleavage are clearly more profound than those seen on transition from active to latent PAI-1. The striking stability of the cleaved substrate mutant of PAI-1 toward thermal and Gdn-HCl induced unfolding suggests a strand insertion comparable with that in wild-type cleaved serpins, despite the presence of a bulky residue at position P-12, previously suggested to prevent insertion.
ISSN: 0006-2960
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory for Pharmaceutical Biology (-)
× corresponding author
# (joint) last author

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