title: Inhibitory effects of cystatins on proteolytic activities of the Plum pox potyvirus cysteine proteinases.
abstract: In an effort to develop new antiviral strategies effective against potyviruses, several cystatins were evaluated for their ability to inhibit the cysteine proteinases of Plum pox potyvirus (PPV) using in vitro proteolytic assays. The following cystatins were purified as GST fusion proteins and shown to be active against papain:oryzacystatins I and II (OCI and OCII), corn cystatin II (CCII), human stefin A (HSA), the domain 8 of tomato multicystatin (TMC-8) and a large 24kDa tomato cystatin (LTCyst). These cystatins did not inhibit the activity of purified recombinant PPV NIa proteinase, a serine-like cysteine proteinases related to the 3C proteinases of picornaviruses and to chymotrypsin. The cystatins were shown to inhibit slightly the activity of the PPV HC-Pro proteinase with CCII being the best inhibitor. However a large excess of the cystatins was required to observe any inhibition. Based on these results and on the documented pleiotropic effects of cystatins on the metabolism of plants, we conclude that they are not the best candidates for antiviral strategies targeted to viral cysteine proteinases. The availability of soluble active recombinant PPV NIa proteinase will be instrumental for the selection of other proteinase inhibitors with increased affinity and specificity for this proteinase.
authors.affiliation: Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC, Canada V0H 1Z0.
authors.forename: Rui
authors.initials: R
authors.lastname: Wen
authors.forename: Shuo Cheng
authors.initials: SC
authors.lastname: Zhang
authors.forename: Dominique
authors.initials: D
authors.lastname: Michaud
authors.forename: Hélène
authors.initials: H
authors.lastname: Sanfaçon
mesh_terms: D015891:Cystatins / Q000302:isolation & purification / Q000494:pharmacology*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D010450:Endopeptidases; D008826:Microbial Sensitivity Tests; D010206:Papain / Q000378:metabolism; D017801:Plum Pox Virus / Q000187:drug effects / Q000201:enzymology*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000494:pharmacology; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D010450:Endopeptidases; C059992:nuclear inclusion protein a, mosaic viruses; D003546:Cysteine Endopeptidases; C072775:HC-Pro protein, potyvirus; D010206:Papain