Probing different conformational states of pregnancy-zone protein. Fluorescence studies utilizing the binding of 4,4'-bis(8-anilino-1-naphthalenesulphonate)

The detection methods currently available for protein aggregation in neurological diseases

Protein aggregation is a pathological feature in various neurodegenerative diseases and is thought to play a crucial role in the onset and progression of neurological disorders. This pathological phenomenon has attracted increasing attention from researchers, but the underlying mechanism has not been fully elucidated yet. Researchers are increasingly interested in identifying chemicals or methods that can effectively detect protein aggregation or maintain protein stability to prevent aggregation formation. To date, several methods are available for detecting protein aggregates, including fluorescence correlation spectroscopy, electron microscopy, and molecular detection methods. Unfortunately, there is still a lack of methods to observe protein aggregation in situ under a microscope. This article reviews the two main aspects of protein aggregation: the mechanisms and detection methods of protein aggregation. The aim is to provide clues for the development of new methods to study this pathological phenomenon.

Interaction of matrix metalloproteinases-2 and -9 with pregnancy zone protein and alpha2-macroglobulin

The binding of matrix metalloproteinases-2 and -9 to pregnancy zone protein and alpha2-macroglobulin was studied. The binding was demonstrated by formation of dimeric as well as tetrameric complexes of pregnancy zone protein and by the formation of alpha2-macroglobulin complexes with fast and intermediate mobility in native gel electrophoresis. The complex formation was confirmed by the use of 125I-labeled matrix metalloproteinase-2. The cleavage sites in the "bait" regions following formation of high-molecular-weight complexes of matrix metalloproteinases with the alpha-macroglobulins were determined by protein sequence analysis. Pregnancy zone protein was cleaved at Thr693-Tyr694 and alpha2-macroglobulin at Gly679-Leu680 and Arg696-Leu697 by matrix metalloproteinase-2. Matrix metalloproteinase-9 cleaved alpha2-macroglobulin at the same site as matrix metalloproteinase-2, but cleavage of pregnancy zone protein was at Leu753-Ser754. The sequences of the bands, visualized in the SDS gel, of approximately 90 and 165 kDa or higher molecular weight complexes were the same. This indicates that the matrix metalloproteinases cleaved the inhibitors with or without binding to them. The present results suggest that matrix metalloproteinases-2 and -9 may interact with pregnancy zone protein and alpha2-macroglobulin in vivo.

Purification of pregnancy zone protein and its receptor binding domain from human plasma

A new significantly improved method for purification of pregnancy zone protein (PZP), alpha 2-macroglobulin (alpha 2M), and the C-terminal PZP receptor binding domain is presented. Several steps in an earlier procedure have been deleted, and modifications in the gradients in the DEAE step leave most of the contaminants bound to a DEAE-Sephacel gel. This procedure makes possible the rapid, simultaneous purification of both of these closely related unstable proteins in native form from human plasma, with no thiolester cleavage or formation of tetrameric PZP. The final preparations of both alpha 2M and PZP are pure as determined by nonreducing and reducing polyacrylamide gel electrophoresis following silver staining and no cross-contamination can be observed. The yield has been significantly improved and typically more than 500 mg PZP can be obtained from 1 liter pregnancy plasma. Furthermore, the stability of PZP at different temperatures on storage was studied. In liquid nitrogen PZP can be maintained in native dimeric form with intact thiolester for many years. The storage of native PZP with intact functional properties during and after purification is an obligatory prerequisite to elucidate the biological role of PZP. The receptor binding domain of PZP can be cleaved from the PZP-methylamine complex by papain and isolated from the other peptides by S-200 gel filtration. The cleavage site was determined and the C-terminal fragment was identified with several site-specific monoclonal antibodies against PZP.

Preparation and characterization of a C-terminal fragment of pregnancy zone protein corresponding to the receptor-binding peptide from human alpha 2-macroglobulin

Digestion of the pregnancy zone protein with papain at pH 4.5 yields an 18 kDa C-terminal fragment. This fragment consists of the 145 C-terminal amino-acid residues cleaved at Asn-1288 Ile and is homologous to the C-terminal receptor binding fragment of human alpha 2-macroglobulin obtained by cleavage with papain. The fragment contains an intrachain disulfide bond between 1308Cys and 1423Cys corresponding to that between 1304Cys and 1419Cys in alpha 2-macroglobulin. An oligosaccharide chain, is present in the C-terminal fragment of pregnancy zone protein as in human alpha 2-macroglobulin. The PZP C-terminal fragment was demonstrated to bind to the LRP/alpha 2M-receptor. Both the pregnancy zone protein and alpha 2-macroglobulin fragments bind three mAb's (alpha 1:1, R35, and 7H11D6) generated against alpha 2-macroglobulin. The mAb 7H11D6 was generated against the alpha 2-macroglobulin-proteinase complex (Isaacs, I.J., Steiner, J.P., Roche, P.A., Pizzo, S.V. and Strickland, D.K. (1988) J. Biol. Chem. 263, 6709-6714) and the binding of this to the C-terminal fragments of both pregnancy zone protein and alpha 2-macroglobulin indicates that both proteins use the same receptor recognition site for binding to the LRP/alpha 2M-receptor.