The Reactive-center Loop of Active PAI-1 is Folded Close to the Protein Core and can be Partially Inserted
2004 (English)In: Journal of Molecular Biology, Vol. 335, no 3, 823-32 p.Article in journal (Refereed) Published
Plasminogen activator inhibitor 1 (PAI-1) is the main inhibitor of plasminogen activators and plays an important role in many pathophysiological processes. Like other members of the serpin family, PAI-1 has a reactive center consisting of a mobile loop (RCL) with P1 and P1′ residues acting as a “bait” for cognate protease. In contrast to the other serpins, PAI-1 loses activity by spontaneous conversion to an inactive latent form. This involves full insertion of the RCL into β-sheet A. To search for molecular determinants that could be responsible for conversion of PAI-1 to the latent form, we studied the conformation of the RCL in active PAI-1 in solution. Intramolecular distance measurements by donor–donor energy migration and probe quenching methods reveal that the RCL is located much closer to the core of PAI-1 than has been suggested by the recently resolved X-ray structures of stable PAI-1 mutants. Disulfide bonds can be formed in double-cysteine mutants with substitutions at positions P11 or P13 of the RCL and neighboring residues in β-sheet A. This suggests that the RCL may be preinserted up to residue P13 in active PAI-1, and possibly even to residue P11. We propose that the close proximity of the RCL to the protein core, and the ability of the loop to preinsert into β-sheet A is a possible reason for PAI-1 being able to convert spontaneously to its latent form.
Place, publisher, year, edition, pages
2004. Vol. 335, no 3, 823-32 p.
fluorescence, donor–donor energy migration, distance measurement, serpin, PAI-1
IdentifiersURN: urn:nbn:se:umu:diva-14769DOI: doi:10.1016/j.jmb.2003.11.005OAI: oai:DiVA.org:umu-14769DiVA: diva2:154441