title: Local transient unfolding of native state PAI-1 associated with serpin metastability.
abstract: The metastability of the native fold makes serpin (serine protease inhibitor) proteins prone to pathological conformational change, often by insertion of an extra β-strand into the central β-sheet A. How this insertion is made possible is a hitherto unresolved question. By the use of advanced hydrogen/deuterium-exchange mass spectrometry (HDX-MS) it is shown that the serpin plasminogen activator inhibitor 1 (PAI-1) transiently unfolds under native condition, on a second-to-minute time scale. The unfolding regions comprise β-strand 5A as well as the underlying hydrophobic core, including β-strand 6B and parts of helices A, B, and C. Based thereon, a mechanism is proposed by which PAI-1 makes transitions through progressively more unfolded states along the reaction coordinate to the inactive, so-called latent form. Our results highlight the profound utility of HDX-MS in detecting sparsely populated, transiently unfolded protein states.
authors: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark).
authors: Morten B
authors: MB
authors: Trelle
authors: Jeppe B
authors: JB
authors: Madsen
authors: Peter A
authors: PA
authors: Andreasen
authors: Thomas J D
authors: TJ
authors: Jørgensen
mesh_terms: D008958:Models, Molecular; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D015843:Serpins
chemical_list: D017395:Plasminogen Activator Inhibitor 1; D015843:Serpins
keywords: hydrogen/deuterium exchange; mass spectrometry; proteins; serpin protein; structure elucidation