A spectroscopic study of the structures of latent, active and reactive-center-cleaved type-1 plasminogen-activator inhibitor.
Type-1 plasminogen-activator inhibitor (PAI-1) was studied by Fourier-transform infrared spectroscopy, far-ultraviolet CD spectroscopy, and fluorescence-emission spectroscopy, with the aim to obtain structural information about its active form. The spectra of latent, active and reactive-center-cleaved forms of PAI-1 produced by HT-1080 cells were different. While the cleaved and the latent forms were similar with regard to their beta-structure content, comparison of the spectra of these forms with the spectra of active PAI-1 suggested a much higher degree of unordered structure for the active form compared with the latent and reactive-center-cleaved forms than previously assumed. We discuss our results with reference to the known three-dimensional X-ray structures of latent PAI-1, of reactive-center-cleaved serpins, including reactive-center-cleaved PAI-1, and of intact serpins, and with reference to previous results on the differences in the affinity of mAbs for the different PAI-1 forms. We interpret our results in favor of a global rearrangement of secondary structure during latency transition and reactive-center cleavage in PAI-1, not only involving the reactive-center loop and parts of beta-sheets A and C, but also the "rear' side of the molecule, such as helices H and G. Thus, we suggest flexibility in serpin structural elements that were previously regarded as rigid.
Schulze
A J
AJ
Max-Planck-Institut für Biochemie, Abteilung Strukturforschung, Planegg-Martinsried, Germany. 106002.3243@compuserve.com
Quarzago
D
D
Andreasen
P A
PA
D001665:Binding Sites; D002460:Cell Line; D002942:Circular Dichroism; D006801:Humans; D066298:In Vitro Techniques; D015394:Molecular Structure; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry* / Q000378:metabolism; D015843:Serpins / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared
D017395:Plasminogen Activator Inhibitor 1; D015843:Serpins