Structures of Active and Latent PAI-1: A Possible Stabilizing Role for Chloride Ions
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- 作者：Thomas J. Stout ; Hugh Graham ; Douglas I. Buckley ; and David J. Matthews
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：July 25, 2000
- 年：2000
- 卷：39
- 期：29
- 页码：8460 - 8469
- 全文大小：328K
- 年卷期：v.39,no.29(July 25, 2000)
- ISSN：1520-4995
文摘
Serpins exhibit a range of physiological roles and can contribute to certain disease statesdependent on their various conformations. Understanding the mechanisms of the large-scale conformationalreorganizations of serpins may lead to a better understanding of their roles in various cardiovasculardiseases. We have studied the serpin, plasminogen activator inhibitor 1 (PAI-1), in both the active andthe latent state and found that anionic halide ions may play a role in the active-to-latent structural transition.Crystallographic analysis of a stable mutant form of active PAI-1 identified an anion-binding site betweenthe central 
-sheet and a small surface domain. A chloride ion was modeled in this site, and its identitywas confirmed by soaking crystals in a bromide-containing solution and calculating a crystallographicdifference map. The anion thus located forms a 4-fold ligated linchpin that tethers the surface domain tothe central -sheet into which the reactive center loop must insert during the active-to-latent transition.Timecourse experiments measuring active PAI-1 stability in the presence of various halide ions showeda clear trend for stabilization of the active form with F- > Cl- > Br- 
I-. We propose that the "stickiness"of this pin (i.e., the electronegativity of the anion) contributes to the energetics of the active-to-latenttransition in the PAI-1 serpin.
-sheet and a small surface domain. A chloride ion was modeled in this site, and its identitywas confirmed by soaking crystals in a bromide-containing solution and calculating a crystallographicdifference map. The anion thus located forms a 4-fold ligated linchpin that tethers the surface domain tothe central -sheet into which the reactive center loop must insert during the active-to-latent transition.Timecourse experiments measuring active PAI-1 stability in the presence of various halide ions showeda clear trend for stabilization of the active form with F- > Cl- > Br- I-. We propose that the "stickiness"of this pin (i.e., the electronegativity of the anion) contributes to the energetics of the active-to-latenttransition in the PAI-1 serpin.